Energy has been both a driving force behind human civilizations and the source of so many conflicts and wars around the world. Today, it remains a major element which guides both economic and political decisions. Yet despite its huge influence on human life, energy remains an immense subject which is, in many ways, a purely abstract one to most of us; after all, nobody has actually seen what a kilowatt-hour looks like (though we may have seen what its output can do in the form of the appliances it powers).This book is designed to provide readers with a general understanding of energy. No background in related fields in higher education are needed. It explores the topic by beginning with what "energy" means and where it comes from; the different forms of energy we currently known and when they were discovered; as well as the innovative breakthroughs and historical milestones which followed their discovery. It then expounds on how each newly discovered form of energy with the use of increased scientific and engineering knowhow needed for these discoveries, and their impacts that have powered our evolution of human civilizations, before arriving at the central concern of the 21st century: how long will humanity's access to energy last?