  The prototype compact group known as Stephan's Quintet (SQ) was observed with
XMM-Newton in order to complement the excellent resolution of Chandra with high
sensitivity to extended emission. SQ is a dynamic environment whose main
effect, at both X-ray and optical wavelengths, appears to be ISM stripping.
This is manifested by: 1) secular evolution of morphological types towards
earlier types and 2) growth of diffuse emission. Virtually all cold, warm and
hot gas in SQ is found outside of the member galaxies. XMM-Newton offers the
opportunity to study the hot gas with unprecedented sensitivity. We find two
main components: 1) extended high surface brightness emission from shocked gas
associated with an ongoing collision and 2) even more extended and unrelaxed
diffuse emission that follows the stripped stellar envelope of the group.
