What have we learned and want to learn from heavy ion collisions at CERN SPS?

The talk is a mini-review of current status of the field, with emphasis on SPS heavy ion program, now and beyond 2000 (as asked by the organizers). Th e main question is, of course, whether we carl convince ourselves and commu nity at large that the QGP is in fact produced at SPS. We came a long way t oward the positive answer, and are definitely on strongly rising part of th e learning curve. Still, in few key directions we lack important pieces of evidences.