diff --git a/src/__tests__/mergeDeep-test.js b/src/__tests__/mergeDeep-test.js
new file mode 100644
index 0000000..09e86c3
--- /dev/null
+++ b/src/__tests__/mergeDeep-test.js
@@ -0,0 +1,82 @@
+import { Map } from 'immutable';
+import mergeDeep from '../mergeDeep';
+
+describe('transmute/mergeDeep', () => {
+  describe('Object', () => {
+    it('merges with an Object', () => {
+      expect(
+        mergeDeep(
+          {
+            one: 3,
+            three: {
+              a: 0,
+              b: 1,
+            },
+          },
+          {
+            one: 1,
+            two: 2,
+            three: {
+              a: 1,
+            },
+          }
+        )
+      ).toMatchSnapshot();
+    });
+
+    it('merges with a Map', () => {
+      expect(
+        mergeDeep(
+          Map({
+            one: 3,
+            three: {
+              a: 1,
+            },
+          }),
+          {
+            one: 1,
+            two: 2,
+            three: {
+              a: 0,
+              b: 1,
+            },
+          }
+        )
+      ).toMatchSnapshot();
+    });
+  });
+
+  describe('Iterable', () => {
+    const merger = mergeDeep({ one: 3, three: 1 });
+
+    it('merges with an Object', () => {
+      expect(
+        merger(
+          Map({
+            one: 1,
+            two: 2,
+            three: {
+              a: 0,
+              b: 1,
+            },
+          })
+        )
+      ).toMatchSnapshot();
+    });
+
+    it('merges with a Map', () => {
+      expect(
+        merger(
+          Map({
+            one: 1,
+            two: 2,
+            three: {
+              a: 0,
+              b: 1,
+            },
+          })
+        )
+      ).toMatchSnapshot();
+    });
+  });
+});
diff --git a/src/mergeDeep.js b/src/mergeDeep.js
new file mode 100644
index 0000000..c9f4428
--- /dev/null
+++ b/src/mergeDeep.js
@@ -0,0 +1,36 @@
+import _reduce from './internal/_reduce';
+import _set from './internal/_set';
+import curry from './curry';
+import isObject from './isObject';
+import isRecord from './isRecord';
+import isArray from './isArray';
+
+function mergeDeep(updates, subject) {
+  console.log({ updates, subject });
+  return _reduce(
+    subject,
+    (acc, value, key) => {
+      if (isObject(value) || isRecord(value)) {
+        return _set(key, mergeDeep(value, subject[key]), acc);
+      }
+      return _set(key, value, acc);
+    },
+    updates
+  );
+}
+
+/**
+ * Takes each entry of `updates` and sets it on `subject`.
+ *
+ * @example
+ * // returns Map { "one" => 3, "two" => 2, "three" => { a: 1, b: 1}}
+ * merge(
+ *   Map({one: 1, two: 2, three: { a: 1 }}),
+ *   Map({one: 3, three: { a: 0, b: 1}})
+ * );
+ *
+ * @param  {Iterable} updates key-value pairs to merge in `subject`.
+ * @param  {Iterable} subject the thing to update.
+ * @return {Iterable} with each key-value of `updates` merged into `subject`.
+ */
+export default curry(mergeDeep);