Time for action — zooming the scene in 3D View
If you need to get a better overview of the scene, or get a closer view, then zooming is what you need:
Move the cursor over the 3D View and push the Ctrl key.
Then press the middle mouse button (MMB) and move the mouse up and down.
What just happened?
To zoom in and out of the 3D View you press the Ctrl key and hold down the middle mouse button (MMB) while you move the cursor up and down over the 3D View.