In this instructable I'll show how to make lightning.

Step 1: Gradient

First off make a gradient going black to white. It doest matter which way its goes.

Step 2: Difference Clouds

Go to Filters> Render> Difference clouds.

Step 3: Invert!

Easy enough, click control+i, or go to image> adjust> invert.

Step 4: Levels

It's kinda looking like lightning already! Now, go to image> adjust> levels (or control+l). Move the middle slider to the right. The farther left it is, the less the clouds reflext. The farther right, the more they reflect.

Step 5: Color!

Make a new layer above the lightning layer. Fill it in with a light blue (alt+backspace). Set the layer mode to overlay (in the layers pallette, right above the little thumbnails).

Step 6: Tada!

Your done your lightning. Play safe and don't electrocute anyone! :D