The launch of ASCA has radically changed the observational situation in high energy astrophysics. With an energy resolution 6 times better than previously available at E > 2 keV, E/Delta E similar to 50 at 6 keV, a bandwidth from 0.4-10 keV, and an increase in sensitivity of a factor of 100 at E > 2 keV compared to previous missions, combined with true X-ray spectral imaging, ASCA has enabled a fundamentally new class of observations.