Batik is a traditional way to dye fabric, usually using hot wax to draw out a design and then dying it over. The wax is a resist for the dye, and when it is removed, it leaves a white or a light colored design. For the above example, the white part of the design is what was covered up initially. For kids, you can just use gel glue to get similar results without the burns!
A drawback to this technique is that it takes overnight for the glue to dry before you can paint/dye on top of it, so there definitely isn't much instant gratification.