Gamma ray astronomy beyond 2001: What instruments for the newt challenges?

In spite of the recent successes of SIGMA, RXTE and Compton GRO, and the la unch of INTEGRAL in 2001, a lot of questions will stay opened for the next decades in gamma-ray astronomy. In this context we have to think about futu re instrument concepts which will allow a new step in the understanding of high-energy phenomena at work in many exciting objects: binary systems with compact objects, active galactic nuclei, supernovae and novae, gamma ray b ursters .. A short overview of these new types of instruments will be given .