My English-speaking friends know me as Greg. I was born in Poland, but my college and graduate education was in the US, respectively at MIT and Harvard. After spending 14 years at NASA/Goddard, I arrived in Stanford in 2000. My research interests are mainly in extragalactic high-energy astrophysics. This includes (1) studies of active galactic nuclei, and an associated formation and evolution of relativistic jets; and (2) studies of clusters of galaxies, and in particular the processes responsible for the heating of the X-ray emitting intra-cluster gas. Besides taking advantage of data from the Fermi Gamma-ray Observatory, I am involved in analyzing and interpreting observations performed with X-ray satellites such as NuSTAR, a recently-launched NASA satellite, sensitive in the hard X-ray band, and Hitomi, a joint Japanese - US X-ray astronomy mission.