I am a theoretical physicist, working mainly on quantum gravity, cosmology, and particle physics. In the past two decades, our understanding of the universe has improved dramatically, including the Nobel-winning discovery of the accelerated expansion. Also, recent progresses in quantum gravity are revealing remarkable natures of spacetime and gravity, beyond what we can learn from quantum field theory in curved spacetime. These new developments together suggest a surprising picture of the “quantum multiverse”: our universe may be one of the many universes in which low energy physical laws take different forms, and that quantum mechanics plays a crucial role in describing these many universes even at the largest distance scales. More recently, I am studying fundamental aspects of quantum gravity, such as the black hole information problem, and their implications for future cosmological observations.