We have developed a tabletop shock compression microscope for studying shock initiation and detonation of energetic materials. This microscope uses a laser to launch 0-5 km/s flyer plates onto tiny charges of plastic explosives (PBX) made in our lab and characterized using electron microscopy and x-ray CT scan. The flyer plates produce short-duration (<20 ns) well-characterized planar shocks. The PBX charges each weigh about 30 ug and are fabricated into a shock target array containing about 200 nominally identical charges. The pressure and shock front are measured by a high-speed photon Doppler velocimeter, and the temperature is measured using a high dynamic range optical pyrometer. We can also photograph the shocked PBX with near-diffraction resolution using a 2 ns camera. The emphasis in this talk will be understanding how microstructure, including voids, influences shock initiation. By obtaining more than 1,000 shock initiation events, we can investigate the variability in the energetic material performance caused by statistical variations in microstructure. We have also tagged the explosive crystals and binder in the PBX with photoemissive nanoparticles which allows us to visualize the shock initiation process at the single grain level.