Where do we come from? Although this is one of the most mysterious philosophical questions from the ancient times, modern science is step by step unveiling its answer. The most popular theory of the origin of our universe may be the hot Big-Bang theory followed by fast-expanding period known as inflation, but still there are some problems remaining. Meanwhile, another scenario called bounce cosmology, which aims at solving these problems, might shed some new light on our beginning time. In this talk, I will review the modelbuildings of bounce cosmology, including the new problems we have encountered and how we struggle to overcome them.