Invisible objects can be used to create unique lighting. If you create a lamp or other light source, It's recommended to paint the light bulb with the unlit material. This is because glow causes strange lighting effects on the objects it touches.

You can then create a cube painted with glow and make it invisible with lighting and shadows turned on. You will also want to turn off collidable, so people don’t bump into it. You can move, and scale the cube to customize the way the light affects your world.

Seen above is using an invisible, non-collidable block painted with the glow material. Make sure the object has light and shadow selected for it to cast the light.