**Abstract:** “How did our universe begin?” is possibly one of the oldest questions that have
bewildered humans throughout history. As a theoretical cosmologist, our job is to find a
mathematically consistent picture for early universe that could explain observations, from
the largest to the smallest scales. The past thirty years have witnessed amazing progress,
both in developing technology for precision cosmological observations, and in perfecting
mathematical methodology to explain them. For example, ripples in cosmic geometry are
now measured with the precision of one part in a million. We also have sophisticated
mathematical frameworks such as general relativity and quantum theories that describe the
origin of these ripples in early universe. However, with all of these extraordinary
achievements, some old and new puzzles remain unsolved. For example we still have not
resolved the most crucial puzzle about the origin of cosmos, namely the Big Bang Singularity
problem. We will take a journey back in time to explore the fascinating realm of early
universe and some of its mysteries.