This first chapter provides an overview of thin films and coatings, reviewing their timeline and increasing relevance in the engineering domain. Thin films that are a number of layers deposited in very small thicknesses have been in use for many years and have undergone various changes. Starting from their initial application in relatively coarse ideas, they successfully evolved and are now critical elements of many important fields. Thin films are applied in electronics, optics and material engineering as these materials enhance the performance, reliability and efficacy of machines and systems. The chapter also provides the state of art on thin films and how this technology has enhanced the development of more accurate as well as efficient coatings. Analyzing the development of thin films, it is possible to understand how these materials evolved from simple tools to the key components of technologies. Although it is the first chapter in this book, it provides the fundamental knowledge about thin films and coatings to help prepare the reader for the remaining chapters that focus on the more detailed aspects of these materials and their applications in engineering.