What is Bitcoin? An apparently simple question that hides a great deal of complexity. Coming to understand Bitcoin in all its magnitude is difficult. Bitcoin is a constantly evolving system that requires knowledge in multiple disciplines. Game theory, philosophy, cryptography, networks and distributed systems, and economic and monetary theory, among others. And while other books on Bitcoin focus on some of the areas of knowledge, creating a narrow view of the concept of Bitcoin, The Fundamentals of Bitcoin aims to give a 360-degree view through a journey divided into four chapters The first chapter delves into the philosophical underpinnings and motivations for the creation of Bitcoin. A long road that begins in the late 80s with significant advances in modern cryptography, followed by a series of attempts to create private digital money by a group of cryptographers and programmers known as the cypherpunks, and with the 2008 financial crisis as a catalyst. The second chapter recounts the events surrounding the publication of the Bitcoin white paper and the network’s launch, the influences that inspired its creation, and its evolution during the first years of existence and until the disappearance of its creator, Satoshi Nakamoto. Finally, the chapter describes the steps for getting started with Bitcoin. From acquisition to receipt, transfer, or tracking bitcoin. The third chapter focuses on the economic and financial fundamentals behind Nakamoto’s invention. It starts by exploring the origin of money, its functions, and the properties necessary for an asset or good to fulfill its mission as money. The chapter also analyzes Bitcoin’s monetary policy and its economic cycles. The fourth and final chapter of the book examines the technical foundations through the study of Bitcoin’s four main components: the peer-to-peer network and its nodes, the blockchain and its transactions, the decentralized system for blocks and transactions verification, and the mining or Proof-of-Work consensus mechanism. The chapter also provides a brief introduction to the Lightning Network, a second-layer solution built on top of Bitcoin. Students in my classes frequently ask me how long it takes me to prepare the sessions where I explain Bitcoin. They refer to the preparation of the material. My response usually surprises them: more than five years and fifteen thousand hours of reading, studying, and building. My classes and this book are intended to help others shorten the learning curve and avoid the misinformation that frequently surrounds this wonderful invention.​ Let me guide you on an incredible journey of learning what Bitcoin is and how it works, the decentralized digital money of the future, and one of the most important inventions of the 21st century.