diff --git a/graphics/opengl/src/main/java/de/staropensource/sosengine/graphics/opengl/OpenGlInternalApi.java b/graphics/opengl/src/main/java/de/staropensource/sosengine/graphics/opengl/OpenGlInternalApi.java
new file mode 100644
index 0000000..233d128
--- /dev/null
+++ b/graphics/opengl/src/main/java/de/staropensource/sosengine/graphics/opengl/OpenGlInternalApi.java
@@ -0,0 +1,33 @@
+/*
+ * STAROPENSOURCE ENGINE SOURCE FILE
+ * Copyright (c) 2024 The StarOpenSource Engine Contributors
+ * Licensed under the GNU Affero General Public License v3
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package de.staropensource.sosengine.graphics.opengl;
+
+import de.staropensource.sosengine.graphics.classes.ApiInternalClass;
+import de.staropensource.sosengine.graphics.classes.Window;
+import org.jetbrains.annotations.NotNull;
+
+public class OpenGlInternalApi implements ApiInternalClass {
+    /** {@inheritDoc} */
+    @Override
+    @NotNull
+    public Class<? extends Window> getWindowClass() {
+        return de.staropensource.sosengine.graphics.opengl.classes.Window.class;
+    }
+}
diff --git a/graphics/opengl/src/main/java/de/staropensource/sosengine/graphics/opengl/OpenGlSubsystem.java b/graphics/opengl/src/main/java/de/staropensource/sosengine/graphics/opengl/OpenGlSubsystem.java
index 860fb57..a34e994 100644
--- a/graphics/opengl/src/main/java/de/staropensource/sosengine/graphics/opengl/OpenGlSubsystem.java
+++ b/graphics/opengl/src/main/java/de/staropensource/sosengine/graphics/opengl/OpenGlSubsystem.java
@@ -31,6 +31,7 @@ import de.staropensource.sosengine.base.types.EventPriority;
 import de.staropensource.sosengine.base.types.logging.LogIssuer;
 import de.staropensource.sosengine.base.utility.Miscellaneous;
 import de.staropensource.sosengine.graphics.GraphicsSubsystem;
+import de.staropensource.sosengine.graphics.classes.ApiInternalClass;
 import de.staropensource.sosengine.graphics.classes.ApiMainClass;
 import de.staropensource.sosengine.graphics.classes.ApiManagementClass;
 import de.staropensource.sosengine.graphics.events.GraphicsApiErrorEvent;
@@ -74,6 +75,18 @@ public final class OpenGlSubsystem implements ApiMainClass {
      */
     private final LoggerInstance logger = new LoggerInstance(new LogIssuer(getClass(), CodePart.ENGINE));
 
+    /**
+     * The Graphics API's internal API class.
+     *
+     * @see ApiInternalClass
+     * @since v1-alpha0
+     *
+     * -- GETTER --
+     * {@inheritDoc}
+     */
+    @Getter
+    private ApiInternalClass internalApi;
+
     /**
      * The Graphics API's management class.
      *
@@ -133,6 +146,7 @@ public final class OpenGlSubsystem implements ApiMainClass {
                 logger.crash("Unable to initialize GLFW");
 
             // Initialize management class
+            internalApi = new OpenGlInternalApi();
             management = new OpenGlManagement();
         });
 
diff --git a/graphics/src/main/java/de/staropensource/sosengine/graphics/classes/ApiInternalClass.java b/graphics/src/main/java/de/staropensource/sosengine/graphics/classes/ApiInternalClass.java
new file mode 100644
index 0000000..f93fcea
--- /dev/null
+++ b/graphics/src/main/java/de/staropensource/sosengine/graphics/classes/ApiInternalClass.java
@@ -0,0 +1,38 @@
+/*
+ * STAROPENSOURCE ENGINE SOURCE FILE
+ * Copyright (c) 2024 The StarOpenSource Engine Contributors
+ * Licensed under the GNU Affero General Public License v3
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package de.staropensource.sosengine.graphics.classes;
+
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * The interface for internal API access, used by the graphics subsystem.
+ *
+ * @since v1-alpha2
+ */
+@SuppressWarnings({ "unused" })
+public interface ApiInternalClass {
+    /**
+     * Returns the {@link Window} class.
+     *
+     * @return {@link Window} class
+     */
+    @NotNull
+    Class<? extends Window> getWindowClass();
+}
diff --git a/graphics/src/main/java/de/staropensource/sosengine/graphics/classes/ApiMainClass.java b/graphics/src/main/java/de/staropensource/sosengine/graphics/classes/ApiMainClass.java
index 5a84fc3..fbb0f53 100644
--- a/graphics/src/main/java/de/staropensource/sosengine/graphics/classes/ApiMainClass.java
+++ b/graphics/src/main/java/de/staropensource/sosengine/graphics/classes/ApiMainClass.java
@@ -50,7 +50,17 @@ public interface ApiMainClass extends SubsystemMainClass {
     String getApiName();
 
     /**
-     * Returns the API's management class.
+     * Returns the Graphics API's internal API access class.
+     *
+     * @return a {@link ApiInternalClass}
+     * @see ApiInternalClass
+     * @since v1-alpha2
+     */
+    @NotNull
+    ApiInternalClass getInternalApi();
+
+    /**
+     * Returns the Graphics API's management class.
      *
      * @return a {@link ApiManagementClass}
      * @see ApiManagementClass