diff --git a/lib/mayo.ex b/lib/mayo.ex
index 3295a6c..db9a9a6 100644
--- a/lib/mayo.ex
+++ b/lib/mayo.ex
@@ -49,7 +49,7 @@ defmodule Mayo do
   end
 
   defp reduce_map_pipes({key, pipes}, acc) do
-    item = quote do: Access.get(result, unquote(key))
+    item = quote do: Mayo.Access.get(result, unquote(key))
     pipe = compile(pipes, item)
 
     quote do
@@ -65,7 +65,7 @@ defmodule Mayo do
               {:error, %{err | paths: [unquote(key) | paths]}}
 
             value ->
-              Access.put(result, unquote(key), value)
+              Mayo.Access.put(result, unquote(key), value)
           end
       end
     end
diff --git a/lib/mayo/access.ex b/lib/mayo/access.ex
new file mode 100644
index 0000000..a0c668a
--- /dev/null
+++ b/lib/mayo/access.ex
@@ -0,0 +1,33 @@
+defmodule Mayo.Access do
+  def fetch(value, key) when is_map(value) do
+    Map.fetch(value, key)
+  end
+
+  def fetch(value, key) when is_list(value) do
+    Keyword.fetch(value, key) 
+  end
+
+  def get(value, key) when is_map(value) do
+    Map.get(value, key)
+  end
+
+  def get(value, key) when is_list(value) do
+    Keyword.get(value, key)
+  end
+
+  def put(value, key, new) when is_map(value) do
+    Map.put(value, key, new)
+  end
+
+  def put(value, key, new) when is_list(value) do
+    Keyword.put(value, key, new)
+  end
+
+  def delete(value, key) when is_map(value) do
+    Map.delete(value, key)
+  end
+
+  def delete(value, key) when is_list(value) do
+    Keyword.delete(value, key)
+  end
+end
diff --git a/lib/mayo/map.ex b/lib/mayo/map.ex
new file mode 100644
index 0000000..5393731
--- /dev/null
+++ b/lib/mayo/map.ex
@@ -0,0 +1,143 @@
+defmodule Mayo.Map do
+  @doc """
+  Checks the minimum number of the keys in the map.
+
+      iex> Mayo.Map.min(%{foo: "bar"}, 1)
+      %{foo: "bar"}
+
+      iex> Mayo.Map.min(%{}, 1)
+      {:error, %Mayo.Error{type: "map.min"}}
+  """
+  def min(value, len) when is_map(value) do
+    if length(Map.keys(value)) < len do
+      {:error, %Mayo.Error{
+        type: "map.min"
+      }}
+    else
+      value
+    end
+  end
+
+  def min(value, _), do: value
+
+  @doc """
+  Checks the maximum number of the keys in the map.
+
+      iex> Mayo.Map.max(%{foo: "bar"}, 1)
+      %{foo: "bar"}
+
+      iex> Mayo.Map.max(%{foo: "bar", baz: "boo"}, 1)
+      {:error, %Mayo.Error{type: "map.max"}}
+  """
+  def max(value, len) when is_map(value) do
+    if length(Map.keys(value)) > len do
+      {:error, %Mayo.Error{
+        type: "map.max"
+      }}
+    else
+      value
+    end
+  end
+
+  def max(value, _), do: value
+
+  @doc """
+  Checks the number of the keys in the map.
+
+      iex> Mayo.Map.length(%{foo: "bar"}, 1)
+      %{foo: "bar"}
+
+      iex> Mayo.Map.length(%{}, 1)
+      {:error, %Mayo.Error{type: "map.length"}}
+  """
+  def length(value, len) when is_map(value) do
+    if length(Map.keys(value)) == len do
+      value
+    else
+      {:error, %Mayo.Error{
+        type: "map.length"
+      }}
+    end
+  end
+
+  def length(value, _), do: value
+
+  @doc """
+  Checks the presence of keys.
+
+      iex> Mayo.Map.with(%{foo: "bar", baz: "boo"}, [:foo, :baz])
+      %{foo: "bar", baz: "boo"}
+
+      iex> Mayo.Map.with(%{foo: "bar"}, [:foo, :baz])
+      {:error, %Mayo.Error{type: "map.with", paths: [:baz]}}
+  """
+  def with(value, peers) when is_map(value) do
+    Enum.reduce peers, value, fn key, acc ->
+      case acc do
+        {:error, _} = err -> err
+
+        _ ->
+          case Map.fetch(acc, key) do
+            :error -> {:error, %Mayo.Error{
+              paths: [key],
+              type: "map.with"
+            }}
+
+            _ -> acc
+          end
+      end
+    end
+  end
+
+  def with(value, _), do: value
+
+  @doc """
+  Forbids the presence of keys.
+
+      iex> Mayo.Map.without(%{foo: "bar"}, [:baz, :boo])
+      %{foo: "bar"}
+
+      iex> Mayo.Map.without(%{foo: "bar", baz: "boo"}, [:baz, :boo])
+      {:error, %Mayo.Error{type: "map.without", paths: [:baz]}}
+  """
+  def without(value, peers) when is_map(value) do
+    Enum.reduce peers, value, fn key, acc ->
+      case acc do
+        {:error, _} = err -> err
+
+        _ ->
+          case Map.fetch(acc, key) do
+            :error -> acc
+
+            _ -> {:error, %Mayo.Error{
+              paths: [key],
+              type: "map.without"
+            }}
+          end
+      end
+    end
+  end
+
+  def without(value, _), do: value
+
+  @doc """
+  Rename a key to another name.
+
+      iex> Mayo.Map.rename(%{foo: "bar"}, :foo, :baz)
+      %{baz: "bar"}
+
+      iex> Mayo.Map.rename(%{foo: "bar"}, :bar, :baz)
+      %{foo: "bar"}
+  """
+  def rename(value, from, to) when is_map(value) do
+    case Map.fetch(value, from) do
+      {:ok, result} ->
+        Map.put(value, to, result)
+        |> Map.delete(from)
+
+      :error -> value
+    end
+  end
+
+  def rename(value, _, _), do: value
+end
diff --git a/test/mayo/map_test.exs b/test/mayo/map_test.exs
new file mode 100644
index 0000000..926d0e5
--- /dev/null
+++ b/test/mayo/map_test.exs
@@ -0,0 +1,4 @@
+defmodule Mayo.MapTest do
+  use ExUnit.Case
+  doctest Mayo.Map
+end
diff --git a/test/mayo_test.exs b/test/mayo_test.exs
index 75f7dd1..6ccd450 100644
--- a/test/mayo_test.exs
+++ b/test/mayo_test.exs
@@ -3,11 +3,13 @@ defmodule MayoTest do
   doctest Mayo
 
   test "map" do
-    result = Mayo.validate %{}, %{
+    result = Mayo.validate %{
+      username: "test"
+    }, %{
       username: Mayo.Any.string |> Mayo.String.min(4)
     }
 
-    assert result == %{}
+    assert result == %{username: "test"}
 
     result = Mayo.validate %{}, %{
       username: Mayo.Any.string |> Mayo.Any.required |> Mayo.String.min(4)
@@ -31,11 +33,13 @@ defmodule MayoTest do
   end
 
   test "keyword list" do
-    result = Mayo.validate [], [
+    result = Mayo.validate [
+      username: "test"
+    ], [
       username: Mayo.Any.string |> Mayo.String.min(4)
     ]
 
-    assert result == []
+    assert result == [username: "test"]
 
     result = Mayo.validate [], [
       username: Mayo.Any.string |> Mayo.Any.required |> Mayo.String.min(4)