Because of the deBroglie wave nature of atoms, many of the phenomena familiar in "photon" optics can also be observed in "atom" optics. These include diffraction, Bragg scattering, and interferometry. With the experimental achievement of Bose-Einstein condensation of atomic gases, we now have coherent atom sources for atom optics analogous to laser sources for photon optics. We have performed a number of wave-optics experiments using Bose condensates, including the first demonstration of non-linear atom optics: four wave mixing of deBroglie waves.