Laser diffraction, how does it work? Allow the monkeys here at GeekLabs to lay some science down on ya: a Diffractive Optical Element (DOE) is a piece of transparent material (generally plastic or glass) with a specially-designed microstructure that acts like a router for photons - directing those little photons this way and that. When a laser beam is pointed through the microstructure of a DOE, BLAM-O! The photons are redirected according to the structure of the DOE, and you get pretty patterns.
This Laser Diffraction Plate Science Kit is one such DOE with several different microstructure elements, so you can play with several examples of what this little bit of awesome science can do. The polycarbonate plastic plate contains several different microstructure patterns, including two star fields, the moon, and even a globe that rotates as the laser beam is moved along the surface. Check out all the cool things you can do with just a laser pointer and a bit of science... and this little DOE kit, of course!