Loop quantum gravity (LQG) had its origins with theories based on the quantum geometries of space-time. Theoretical physics has been working towards developing a theory of everything (TOE) for decades. The spirit of the effort appears to have a basis in fact as experimental evidence from The Large Hadron Collider and The Hubble Telescope continue to provide pieces of information that both confirm theories (Higgs Boson) and continue to raise new and confounding issues such as Dark Matter and Dark Energy. LQG is a remarkable attempt to incorporate the math of quantum mechanics and Einstein's theory of general relativity. A major focus is on developing the math of the geometric "granularity" or quantization of space. The fundamental concept behind LQG is that space is mathematically modeled as a very fine interconnected network of finite loops. These 'loops' form structures on the order of a Planck Length which is approximately 10 -35 meters. There are basically two variations being explored in LQG with one being canonical loop quantum gravity and a more recent variant known as covariant loop quantum gravity or 'spin-foam' theory. LQG is also being applied to the field of cosmology and is termed Loop Quantum Cosmology (LQC). This book is designed to be a reference and provide an overview of the topic and give the reader a structured knowledge to familiarize yourself with the topic at the most affordable price possible. The accuracy and knowledge is of an international viewpoint as the edited articles represent the inputs of many knowledgeable individuals and some of the most current knowledge on the topic, based on the date of publication.