The study of the universe, its origin, evolution and future is under the scope of cosmology. Astronomy is the science concerned with celestial objects such as stars, galaxies, planets, gamma ray bursts, etc. and their associated phenomena, origin and evolution. Cosmology deals with the universe as a whole, while astronomy studies individual celestial objects of the universe. Astrophysics is a branch of astronomy, which integrates the principles of physics and chemistry for the study of the nature of astronomical objects. The objects studied in astrophysics are stars, extrasolar planets, galaxies, cosmic microwave background and the interstellar medium. The studies of these are approached from both theoretical and observational astrophysics. This book is a compilation of chapters that discuss the most vital concepts and emerging trends in the fields of cosmology, astrophysics and astronomy. Different approaches, evaluations, methodologies and advanced studies in these fields have been included in this book. It is meant for students who are looking for an elaborate reference text on these domains.