Sean Carroll is a physicist at Caltech. His research includes theoretical physics and astrophysics, especially cosmology, field theory, and gravitation. He has published several research papers dark matter and dark energy, modified gravity, violations of Lorentz invariance, extra dimensions, topological defects, cosmic microwave background anisotropies, causality violation, black holes, and the cosmological constant problem. He is currently focused on origin of the universe and the arrow of time, including the roles of inflation, baby universes, and quantum gravity.
In his recent video by Techinsider, he explains what existed before Big Bang and it actually means. So watch and learn: