GLAST Mission

The upcoming GLAST mission represents a major step forward in gamma-ray astronomy in sensitivity and angular resolution. X-ray astronomy has gone through a similar revolution in the last 40 years increasing sensitivity by 8 orders of magnitude and angular resolution by 3 orders of magnitude. Many of the discoveries of x-ray astronomy have been unanticipated and serendiptious and can provide a good guide to the sort of discovery space accessible to GLAST. I will concentrate on 2 areas of science AGN evolution and clusters of galaxies and the implications for GLAST from recent x-ray results.