Prof. Cui carries out research in the general areas of high energy astrophysics and particle astrophysics. At present the science topics of particular interest include: (1) mass accretion and particle acceleration in microquasars and AGN; and (2) warm-hot phases of interstellar, circumgalactic, and intergalactic media. He has played key roles in the development of the Rossi X-ray Timing Explorer (RXTE) satellite and the Very Energetic Radiation Imaging Telescope Array (VERITAS) observatory, and is involved in the formulation of several mission concepts. In particular, he presently leads R&D efforts for the Hot Universe Baryon Surveyor (HUBS), which aims at finding “missing baryons” in circumgalactic and intergalactic media via high throughput, high-resolution X-ray spectroscopy.