1.
a. Create a document which is about 500x500 and press D to reset colors.
b. Choose the Gradient Tool and use the "Foreground to Background" gradient.
c. Use Linear Gradient and set Mode to Difference and Opacity to 100%.
2.
a. Now just click around like crazy, like about 30 times until it looks something like this:
b. When you are done with that part go to Filter, Stylize, Find Edges.
c. Now create a New Layer and do what you just did again, click around like a maniac and then press Ctrl+F (Filter, Stylize, Find Edges)
3.
a. Now set the top layer (Layer 2) to Overlay and go to Image, Adjustments, Levels and do following:
b. Done! But now we need some color, I prefer you go to Image, Adjustments, Gradient Map... and feel free to use my gradient, just be sure to mark Reverse!
Black (#000000) Position 0%
Red (#FF3C00) Position 50%
Yellow (#FFF000) Position 75%
White (#FFFFFF) Position 100%
There you go. Hope you like it.
More Tutorials: 
