  With the unequalled INTEGRAL observatory, ESA has provided a unique tool to
the astronomical community that has made Europe the world leader in the field
of gamma-ray astronomy. INTEGRAL provides an unprecedented survey of the soft
gamma-ray sky, revealing hundreds of sources of different kinds, new classes of
objects, extraordinary views of antimatter annihilation in our Galaxy, and
fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the
longly awaited global overview over the soft gamma-ray sky, there is a growing
need to perform deeper, more focused investigations of gamma-ray sources,
comparable to the step that has been taken in X-rays by going from the ROSAT
survey satellite to the more focused XMM-Newton observatory. Technological
advances in the past years in the domain of gamma-ray focusing using Laue
diffraction techniques have paved the way towards a future European gamma-ray
mission, that will outreach past missions by large factors in sensitivity and
angular resolution. Such a future Gamma-Ray Imager will allow to study particle
acceleration processes and explosion physics in unprecedented depth, providing
essential clues on the intimate nature of the most violent and most energetic
processes in the Universe.
