Dr. Hui Li is a tenure-track assistant professor in Tsinghua University. He was a Hubble fellow at Columbia and MIT. He obtained his PhD at the University of Michigan. Hui's research interests include galaxy formation, evolution of giant molecular clouds and formation of most massive star clusters, origin of globular clusters in different types of galaxies, stellar dynamics of globular clusters, gamma-rays from supernova remnants and pulsar wind nebulae, etc.The cycling of gas in and around galaxies plays a critical role in their evolution. For galaxies smaller than the Milky Way, the complex baryonic cycle is believed to be driven by feedback from young stars. To fully understand this highly non-linear process, it is necessary to employ multi-scale, multi-physics simulations. In this talk, I will first provide a brief overview of the current state of galaxy formation simulations. I will then emphasize the importance of ionizing feedback from young stars, which has largely been overlooked in previous simulations due to its immense computational costs. Lastly, I will present some of our recent work that uses state-of-the-art radiation hydrodynamics simulations to investigate how different stellar feedback processes affect the properties of the star formation activities, the interstellar medium, and the circumgalactic medium.