diff --git a/README.org b/README.org
index 94e336d..a6a3bdb 100644
--- a/README.org
+++ b/README.org
@@ -1184,3 +1184,44 @@
     #+END_SRC
 
 
+*** =<T> Either<T, R> flatMapLeft(Function<L, Either<T, R>> f)=
+
+    FlatMap the function across the left value.
+
+    #+being_src java
+    Either<Integer, String> either = Either.left(2);
+    Either<Integer, String> resultLeft = either.flatMapLeft(l -> Either.left(l * 2));
+    Either<Integer, String> resultRight = either.flatMapLeft(l -> Either.right(l * 2));
+    #+end_src
+
+
+*** =<T> Either<T, R> flatMapRight(Function<L, Either<T, R>> f)=
+
+    FlatMap the function across the right value.
+
+    #+being_src java
+    Either<Integer, String> either = Either.right("2");
+    Either<Integer, String> resultLeft = either.flatMapRight(l -> Either.left(l * 2));
+    Either<Integer, String> resultRight = either.flatMapRight(l -> Either.right(l * 2));
+    #+end_src
+
+
+*** =Optional<L> getLeft()=
+
+    Returns an Optional containing the left value, if is a left, otherwise returns an empty Optional.
+
+    #+being_src java
+    Either<Integer, String> either = Either.right("2");
+    Optional<Integer> left = either.getLeft();
+    #+end_src
+
+
+*** =Optional<R> getRight()=
+
+    Returns an Optional containing the right value, if is a right, otherwise returns an empty Optional.
+
+    #+being_src java
+    Either<Integer, String> either = Either.right("2");
+    Optional<String> right = either.getRight();
+    #+end_src
+
diff --git a/src/main/java/net/kemitix/mon/experimental/either/Either.java b/src/main/java/net/kemitix/mon/experimental/either/Either.java
index 92ed29f..216fd1e 100644
--- a/src/main/java/net/kemitix/mon/experimental/either/Either.java
+++ b/src/main/java/net/kemitix/mon/experimental/either/Either.java
@@ -21,6 +21,7 @@
 
 package net.kemitix.mon.experimental.either;
 
+import java.util.Optional;
 import java.util.function.Consumer;
 import java.util.function.Function;
 
@@ -31,6 +32,7 @@ import java.util.function.Function;
  * @param <R> the type of the Either for right value
  * @author Paul Campbell (pcampbell@kemitix.net)
  */
+@SuppressWarnings("methodcount")
 public interface Either<L, R> {
 
     /**
@@ -96,4 +98,38 @@ public interface Either<L, R> {
      * @return a new Either
      */
     public abstract <T> Either<L, T> mapRight(Function<R, T> f);
+
+    /**
+     * FlatMap the function across the left value.
+     *
+     * @param f   the function to apply to any left value
+     * @param <T> the type to change the left value to
+     * @return a new Either if is a Left, else this
+     */
+    public abstract <T> Either<T, R> flatMapLeft(Function<L, Either<T, R>> f);
+
+    /**
+     * FlatMap the function across the right value.
+     *
+     * @param f   the function to apply to any right value
+     * @param <T> the type to change the right value to
+     * @return a new Either if is a Right, else this
+     */
+    public abstract <T> Either<L, T> flatMapRight(Function<R, Either<L, T>> f);
+
+    /**
+     * Returns an Optional containing the left value, if is a left, otherwise
+     * returns an empty Optional.
+     *
+     * @return An Optional containing any left value
+     */
+    public abstract Optional<L> getLeft();
+
+    /**
+     * Returns an Optional containing the right value, if is a right, otherwise
+     * returns an empty Optional.
+     *
+     * @return An Optional containing any right value
+     */
+    public abstract Optional<R> getRight();
 }
diff --git a/src/main/java/net/kemitix/mon/experimental/either/Left.java b/src/main/java/net/kemitix/mon/experimental/either/Left.java
index 7b13fe2..7946e80 100644
--- a/src/main/java/net/kemitix/mon/experimental/either/Left.java
+++ b/src/main/java/net/kemitix/mon/experimental/either/Left.java
@@ -23,6 +23,7 @@ package net.kemitix.mon.experimental.either;
 
 import lombok.RequiredArgsConstructor;
 
+import java.util.Optional;
 import java.util.function.Consumer;
 import java.util.function.Function;
 
@@ -62,4 +63,25 @@ class Left<L, R> implements Either<L, R> {
     public <T> Either<L, T> mapRight(final Function<R, T> f) {
         return new Left<>(value);
     }
+
+    @Override
+    public <T> Either<T, R> flatMapLeft(final Function<L, Either<T, R>> f) {
+        return f.apply(value);
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public <T> Either<L, T> flatMapRight(final Function<R, Either<L, T>> f) {
+        return (Either<L, T>) this;
+    }
+
+    @Override
+    public Optional<L> getLeft() {
+        return Optional.ofNullable(value);
+    }
+
+    @Override
+    public Optional<R> getRight() {
+        return Optional.empty();
+    }
 }
diff --git a/src/main/java/net/kemitix/mon/experimental/either/Right.java b/src/main/java/net/kemitix/mon/experimental/either/Right.java
index aeadb10..bdffa7d 100644
--- a/src/main/java/net/kemitix/mon/experimental/either/Right.java
+++ b/src/main/java/net/kemitix/mon/experimental/either/Right.java
@@ -23,6 +23,7 @@ package net.kemitix.mon.experimental.either;
 
 import lombok.RequiredArgsConstructor;
 
+import java.util.Optional;
 import java.util.function.Consumer;
 import java.util.function.Function;
 
@@ -62,4 +63,26 @@ class Right<L, R> implements Either<L, R> {
     public <T> Either<L, T> mapRight(final Function<R, T> f) {
         return new Right<>(f.apply(value));
     }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public <T> Either<T, R> flatMapLeft(final Function<L, Either<T, R>> f) {
+        return (Either<T, R>) this;
+    }
+
+    @Override
+    public <T> Either<L, T> flatMapRight(final Function<R, Either<L, T>> f) {
+        return f.apply(value);
+    }
+
+    @Override
+    public Optional<L> getLeft() {
+        return Optional.empty();
+    }
+
+    @Override
+    public Optional<R> getRight() {
+        return Optional.ofNullable(value);
+    }
+
 }
diff --git a/src/test/java/net/kemitix/mon/EitherTest.java b/src/test/java/net/kemitix/mon/EitherTest.java
index 7fd835f..a67b531 100644
--- a/src/test/java/net/kemitix/mon/EitherTest.java
+++ b/src/test/java/net/kemitix/mon/EitherTest.java
@@ -2,113 +2,396 @@ package net.kemitix.mon;
 
 import net.kemitix.mon.experimental.either.Either;
 import org.assertj.core.api.WithAssertions;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 
+import java.time.Instant;
+import java.util.Optional;
+import java.util.function.BiFunction;
+
 class EitherTest implements WithAssertions {
-
-    @Test
-    void whenLeft_isLeft() {
-        //when
-        final Either<Integer, String> either = Either.left(1);
-        //then
-        assertThat(either.isLeft()).isTrue();
+    @Nested
+    @DisplayName("isLeft()")
+    public class IsLeft {
+        @Test
+        void whenLeft_isLeft() {
+            //when
+            final Either<Integer, String> either = Either.left(1);
+            //then
+            assertThat(either.isLeft()).isTrue();
+        }
+        @Test
+        void whenRight_isNotLeft() {
+            //when
+            final Either<Integer, String> either = Either.right("1");
+            //then
+            assertThat(either.isLeft()).isFalse();
+        }
     }
-
-    @Test
-    void whenLeft_isNotRight() {
-        //when
-        final Either<Integer, String> either = Either.left(1);
-        //then
-        assertThat(either.isRight()).isFalse();
+    @Nested
+    @DisplayName("isRight()")
+    public class IsRight {
+        @Test
+        void whenLeft_isNotRight() {
+            //when
+            final Either<Integer, String> either = Either.left(1);
+            //then
+            assertThat(either.isRight()).isFalse();
+        }
+        @Test
+        void whenRight_isRight() {
+            //when
+            final Either<Integer, String> either = Either.right("1");
+            //then
+            assertThat(either.isRight()).isTrue();
+        }
     }
-
-    @Test
-    void whenRight_isNotLeft() {
-        //when
-        final Either<Integer, String> either = Either.right("1");
-        //then
-        assertThat(either.isLeft()).isFalse();
+    @Nested
+    @DisplayName("match()")
+    public class Match {
+        @Test
+        void whenLeft_matchLeft() {
+            //given
+            final Either<Integer, String> either = Either.left(1);
+            //then
+            either.match(
+                    left -> assertThat(left).isEqualTo(1),
+                    right -> fail("Not a right")
+            );
+        }
+        @Test
+        void whenRight_matchRight() {
+            //given
+            final Either<Integer, String> either = Either.right("1");
+            //then
+            either.match(
+                    left -> fail("Not a left"),
+                    right -> assertThat(right).isEqualTo("1")
+            );
+        }
     }
-
-    @Test
-    void whenRight_isRight() {
-        //when
-        final Either<Integer, String> either = Either.right("1");
-        //then
-        assertThat(either.isRight()).isTrue();
+    @Nested
+    @DisplayName("mapLeft()")
+    public class MapLeft {
+        @Test
+        void givenLeft_whenMapLeft_thenMap() {
+            //given
+            final Either<Integer, String> either = Either.left(2);
+            //when
+            final Either<Integer, String> result = either.mapLeft(l -> l * 2);
+            //then
+            result.match(
+                    left -> assertThat(left).isEqualTo(4),
+                    right -> fail("Not a right")
+            );
+        }
+        @Test
+        void givenRight_whenMapLeft_thenDoNothing() {
+            //given
+            final Either<Integer, String> either = Either.right("2");
+            //when
+            final Either<Integer, String> result = either.mapLeft(l -> l * 2);
+            //then
+            result.match(
+                    left -> fail("Not a left"),
+                    right -> assertThat(right).isEqualTo("2")
+            );
+        }
     }
-
-    @Test
-    void whenLeft_matchLeft() {
-        //given
-        final Either<Integer, String> either = Either.left(1);
-        //then
-        either.match(
-                left -> assertThat(left).isEqualTo(1),
-                right -> fail("Not a right")
-        );
+    @Nested
+    @DisplayName("mapRight()")
+    public class MapRight {
+        @Test
+        void givenRight_whenMapRight_thenMap() {
+            //given
+            final Either<Integer, String> either = Either.right("2");
+            //when
+            final Either<Integer, String> result = either.mapRight(l -> l + "2");
+            //then
+            result.match(
+                    left -> fail("Not a left"),
+                    right -> assertThat(right).isEqualTo("22")
+            );
+        }
+        @Test
+        void givenLeft_whenMapRight_thenDoNothing() {
+            //given
+            final Either<Integer, String> either = Either.left(2);
+            //when
+            final Either<Integer, String> result = either.mapRight(r -> r + "x");
+            //then
+            result.match(
+                    left -> assertThat(left).isEqualTo(2),
+                    right -> fail("Not a right")
+            );
+        }
     }
-
-    @Test
-    void whenRight_matchRight() {
-        //given
-        final Either<Integer, String> either = Either.right("1");
-        //then
-        either.match(
-                left -> fail("Not a left"),
-                right -> assertThat(right).isEqualTo("1")
-        );
+    @Nested
+    @DisplayName("flatMapLeft()")
+    public class FlatMapLeft {
+        @Test
+        void givenLeft_whenFlatMapLeft_whenResultLeft_thenIsNewLeft() {
+            //given
+            Either<Integer, String> either = Either.left(2);
+            //when
+            Either<Integer, String> result = either.flatMapLeft(l -> Either.left(l * 2));
+            //then
+            result.match(
+                    left -> assertThat(left).isEqualTo(4),
+                    right -> fail("Not a right")
+            );
+        }
+        @Test
+        void givenLeft_whenFlatMapLeft_whenResultRight_thenIsRight() {
+            //given
+            Either<Integer, String> either = Either.left(2);
+            //when
+            Either<Integer, String> result = either.flatMapLeft(l -> Either.right("recovered"));
+            //then
+            result.match(
+                    left -> fail("Not a left"),
+                    right -> assertThat(right).isEqualTo("recovered")
+            );
+        }
+        @Test
+        void givenRight_whenFlatMapLeft_thenDoNothing() {
+            //given
+            Either<Integer, String> either = Either.right("2");
+            //when
+            Either<Integer, String> result = either.flatMapLeft(l -> Either.left(l * 2));
+            //then
+            result.match(
+                    left -> fail("Not a left"),
+                    right -> assertThat(right).isEqualTo("2")
+            );
+        }
     }
-
-    @Test
-    void givenLeft_whenMapLeft_thenMap() {
-        //given
-        final Either<Integer, String> either = Either.left(2);
-        //when
-        final Either<Integer, String> result = either.mapLeft(l -> l * 2);
-        //then
-        result.match(
-                left -> assertThat(left).isEqualTo(4),
-                right -> fail("Not a right")
-        );
+    @Nested
+    @DisplayName("flatMapRight()")
+    public class FlatMapRight {
+        @Test
+        void givenLeft_whenFlatMapRight_thenDoNothing() {
+            //given
+            Either<Integer, String> either = Either.left(2);
+            //when
+            Either<Integer, String> result = either.flatMapRight(l -> Either.right(l + "2"));
+            //then
+            result.match(
+                    left -> assertThat(left).isEqualTo(2),
+                    right -> fail("Not a right")
+            );
+        }
+        @Test
+        void givenRight_whenFlatMapRight_whenResultRight_thenIsNewRight() {
+            //given
+            Either<Integer, String> either = Either.right("2");
+            //when
+            Either<Integer, String> result = either.flatMapRight(l -> Either.right(l + "2"));
+            //then
+            result.match(
+                    left -> fail("Not a left"),
+                    right -> assertThat(right).isEqualTo("22")
+            );
+        }
+        @Test
+        void givenRight_whenFlatMapRight_whenResultLeft_thenIsLeft() {
+            //given
+            Either<Integer, String> either = Either.right("2");
+            //when
+            Either<Integer, String> result = either.flatMapRight(l -> Either.left(7));
+            //then
+            result.match(
+                    left -> assertThat(left).isEqualTo(7),
+                    right -> fail("Not a right")
+            );
+        }
     }
+    @Nested @DisplayName("getLeft") public class GetLeft {
+        @Test
+        @DisplayName("")
+        public void whenLeft_thenGetValue() {
+            //given
+            Either<String, Integer> either = Either.left("value");
+            //when
+            Optional<String> left = either.getLeft();
+            //then
+            assertThat(left).contains("value");
+        }
 
-    @Test
-    void givenRight_whenMapRight_thenMap() {
-        //given
-        final Either<Integer, String> either = Either.right("2");
-        //when
-        final Either<Integer, String> result = either.mapRight(l -> l + "2");
-        //then
-        result.match(
-                left -> fail("Not a left"),
-                right -> assertThat(right).isEqualTo("22")
-        );
+        @Test
+        @DisplayName("")
+        public void whenRight_thenGetEmpty() {
+            //given
+            Either<Integer, String> either = Either.right("value");
+            //when
+            Optional<Integer> left = either.getLeft();
+            //then
+            assertThat(left).isEmpty();
+        }
     }
+    @Nested @DisplayName("getRight") public class GetRight {
+        @Test
+        @DisplayName("")
+        public void whenLeft_thenGetEmpty() {
+            //given
+            Either<String, Integer> either = Either.left("value");
+            //when
+            Optional<Integer> left = either.getRight();
+            //then
+            assertThat(left).isEmpty();
+        }
 
-    @Test
-    void givenLeft_whenMapRight_thenDoNothing() {
-        //given
-        final Either<Integer, String> either = Either.left(2);
-        //when
-        final Either<Integer, String> result = either.mapRight(r -> r + "x");
-        //then
-        result.match(
-                left -> assertThat(left).isEqualTo(2),
-                right -> fail("Not a right")
-        );
-    }
-
-    @Test
-    void givenRight_whenMapLeft_thenDoNothing() {
-        //given
-        final Either<Integer, String> either = Either.right("2");
-        //when
-        final Either<Integer, String> result = either.mapLeft(l -> l * 2);
-        //then
-        result.match(
-                left -> fail("Not a left"),
-                right -> assertThat(right).isEqualTo("2")
-        );
+        @Test
+        @DisplayName("")
+        public void whenRight_thenGetValue() {
+            //given
+            Either<Integer, String> either = Either.right("value");
+            //when
+            Optional<String> left = either.getRight();
+            //then
+            assertThat(left).contains("value");
+        }
     }
+//    @Nested
+//    @DisplayName("compose()")
+//    public class Compose {
+//
+//        BiFunction<String, String, Either<String, Integer>> leftToLeftComposer =
+//                (la, lb) -> Either.left(la + lb);
+//
+//        BiFunction<String, String, Either<String, Integer>> leftToRightComposer =
+//                (la, lb) -> Either.right(Integer.parseInt(la) + Integer.parseInt(lb));
+//
+//        BiFunction<Integer, Integer, Either<String, Integer>> rightToLeftComposer =
+//                (la, lb) -> Either.left("" + la + lb);
+//
+//        BiFunction<Integer, Integer, Either<String, Integer>> rightToRightComposer =
+//                (la, lb) -> Either.right(la + lb);
+//
+//        @Test
+//        public void givenRightAndRight_whenComposeRight_then() {
+//            //given
+//            Either<String, Integer> ea = Either.right(3);
+//            Either<String, Integer> eb = Either.right(7);
+//            //when
+//            Either<String, Integer> result = ea.compose(eb,
+//                    leftToRightComposer,
+//                    rightToRightComposer);
+//            //then
+//            result.match(
+//                    left -> fail("Not a left"),
+//                    right -> assertThat(right).isEqualTo(10)
+//            );
+//        }
+//
+//        @Test
+//        public void givenRightAndRight_whenComposeLeft_then() {
+//            //given
+//            Either<String, Integer> ea = Either.right(3);
+//            Either<String, Integer> eb = Either.right(7);
+//            //when
+//            Either<String, Integer> result = ea.compose(eb,
+//                    leftToLeftComposer,
+//                    rightToLeftComposer);
+//            //then
+//            result.match(
+//                    left ->  assertThat(left).isEqualTo("a+b"),
+//                    right -> fail("Not a right")
+//            );
+//        }
+//        // compose left with left
+//        @Test
+//        public void givenLeftAndLeft_whenComposeRight_then() {
+//            //given
+//            Either<String, Integer> ea = Either.left("3");
+//            Either<String, Integer> eb = Either.left("7");
+//            //when
+//            Either<String, Integer> result = ea.compose(eb,
+//                    leftToRightComposer,
+//                    rightToRightComposer);
+//            //then
+//            result.match(
+//                    left -> fail("Not a left"),
+//                    right -> assertThat(right).isEqualTo(10)
+//            );
+//        }
+//        @Test
+//        public void givenLeftAndLeft_whenComposeLeft_then() {
+//            //given
+//            Either<String, Integer> ea = Either.left("3");
+//            Either<String, Integer> eb = Either.left("7");
+//            //when
+//            Either<String, Integer> result = ea.compose(eb,
+//                    leftToLeftComposer,
+//                    rightToLeftComposer);
+//            //then
+//            result.match(
+//                    left -> fail("Not a left"),
+//                    right -> assertThat(right).isEqualTo(10)
+//            );
+//        }
+//        // compose left with right
+//        @Test
+//        public void givenLeftAndRight_whenComposeRight_then() {
+//            //given
+//            Either<String, Integer> ea = Either.left("3");
+//            Either<String, Integer> eb = Either.right(7);
+//            //when
+//            Either<String, Integer> result = ea.compose(eb,
+//                    leftToRightComposer,
+//                    rightToRightComposer);
+//            //then
+//            result.match(
+//                    left -> fail("Not a left"),
+//                    right -> assertThat(right).isEqualTo(10)
+//            );
+//        }
+//        @Test
+//        public void givenLeftAndRight_whenComposeLeft_then() {
+//            //given
+//            Either<String, Integer> ea = Either.left("3");
+//            Either<String, Integer> eb = Either.right(7);
+//            //when
+//            Either<String, Integer> result = ea.compose(eb,
+//                    leftToLeftComposer,
+//                    rightToLeftComposer);
+//            //then
+//            result.match(
+//                    left -> fail("Not a left"),
+//                    right -> assertThat(right).isEqualTo(10)
+//            );
+//        }
+//        // compose right with left
+//        @Test
+//        public void givenRightAndLeft_whenComposeRight_then() {
+//            //given
+//            Either<String, Integer> ea = Either.right(3);
+//            Either<String, Integer> eb = Either.left("7");
+//            //when
+//            Either<String, Integer> result = ea.compose(eb,
+//                    leftToRightComposer,
+//                    rightToRightComposer);
+//            //then
+//            result.match(
+//                    left -> fail("Not a left"),
+//                    right -> assertThat(right).isEqualTo(10)
+//            );
+//        }
+//        @Test
+//        public void givenRightAndLeft_whenComposeLeft_then() {
+//            //given
+//            Either<String, Integer> ea = Either.right(3);
+//            Either<String, Integer> eb = Either.left("7");
+//            //when
+//            Either<String, Integer> result = ea.compose(eb,
+//                    leftToLeftComposer,
+//                    rightToLeftComposer);
+//            //then
+//            result.match(
+//                    left -> fail("Not a left"),
+//                    right -> assertThat(right).isEqualTo(10)
+//            );
+//        }
+//    }
 }
diff --git a/src/test/java/net/kemitix/mon/tree/MutableTreeTest.java b/src/test/java/net/kemitix/mon/tree/MutableTreeTest.java
index 2092321..e4ff76e 100644
--- a/src/test/java/net/kemitix/mon/tree/MutableTreeTest.java
+++ b/src/test/java/net/kemitix/mon/tree/MutableTreeTest.java
@@ -86,7 +86,7 @@ class MutableTreeTest implements WithAssertions {
                 asList(
                         MutableTree.leaf(sid2),
                         MutableTree.leaf(sid3)));
-        assertThat(result).isEqualToComparingFieldByFieldRecursively(expectedTree);
+        assertThat(result).usingRecursiveComparison().isEqualTo(expectedTree);
     }
 
     @Test
diff --git a/src/test/java/net/kemitix/mon/tree/TreeBuilderTest.java b/src/test/java/net/kemitix/mon/tree/TreeBuilderTest.java
index 4a2a89a..bb64e5f 100644
--- a/src/test/java/net/kemitix/mon/tree/TreeBuilderTest.java
+++ b/src/test/java/net/kemitix/mon/tree/TreeBuilderTest.java
@@ -65,7 +65,7 @@ class TreeBuilderTest {
         final Tree<Node> result = rootBuilder.build();
         //then
         assertThat(result.count()).isEqualTo(3);
-        assertThat(result).isEqualToComparingFieldByFieldRecursively(
+        assertThat(result).usingRecursiveComparison().isEqualTo(
                 MutableTree.of(rootNode, Collections.singleton(
                         MutableTree.of(childNode, Collections.singleton(
                                 MutableTree.leaf(grandchildNode))))));
@@ -86,7 +86,7 @@ class TreeBuilderTest {
                         .build();
         //then
         assertThat(result.count()).isEqualTo(4);
-        assertThat(result).isEqualToComparingFieldByFieldRecursively(
+        assertThat(result).usingRecursiveComparison().isEqualTo(
                 MutableTree.of(rootNode, asList(
                         MutableTree.leaf(child1Node),
                         MutableTree.leaf(child2Node),