Kaaret’s main interest is understanding the intense gravitational fields surrounding black holes and neutron stars and the dynamics of the accretion of matter onto these objects. He builds instrumentation for the X-ray and gamma-ray bands and conducts observations at X-ray, gamma-ray, optical, and radio wavelengths of objects in our Milky Way galaxy and in relatively nearby galaxies. His current work concerns the highly luminous X-ray sources in nearby galaxies which have been interpreted as being intermediate-mass or “medium-sized” black holes, jet ejection from black holes, and the construction of NASA’s new mission for X-ray polarimetry the Gravity and Extreme Magnetism Small Explorer (GEMS).