The most successful scientific theory today about the origin and evolution of the universe is known as the standard Big Bang model, which is one of the most ambitious intellectual constructions of the humanity. It is based on two consolidated branches of theoretical physics, namely, the theory of General Relativity and the Standard Model of particle physics, and is able to make robust predictions, some of them being already confirmed by very precise observations. However, this model is not able to explain some questions raised by observational evidence, such as early inflation of the universe, dark matter and dark energy. This book makes an overview of some of the features of the standard cosmology, and also includes a few original models proposed to solve some of the shortcomings of the standard cosmology, as possible extensions of the Big Bang model. The models, published as articles in scientific journals, introduce new symmetries, fields and particles in order to explain inflation, dark energy and dark matter, separately or in a unified description. The book is addressed especially to PhD students, but also to anyone who is interested in cosmology and astroparticle theory.