Entering fullscreen mode in Unity 3D game view can enhance the immersive experience for players. To achieve this, follow these simple steps:

1. Open Unity 3D: Launch Unity 3D and load your game project.

2. Select Game tab: In the top menu, click on the 'Game' tab to access the Game view.

3. Maximize Game view: Look for the maximize button in the top-right corner of the Game view window. Click on it to expand the view to fullscreen mode.

4. Exit fullscreen mode: To exit fullscreen mode, simply press the 'Esc' key on your keyboard or locate the minimize button in the top-right corner of the Game view window and click on it.

5. Adjust display settings: If you encounter any display issues while in fullscreen mode, you can adjust the display settings within Unity 3D by navigating to Edit > Project Settings > Player and modifying the resolution and fullscreen mode options.

By following these steps, you can easily enter fullscreen mode in Unity 3D game view and enjoy a more immersive gaming experience.