A lot of activity has been taking place in the research community over the decades to efficiently harness solar energy. One way this is fuelled is by the support from the governments which promote the implementation of large-scale projects—whether it be for electric power generation (using PV), or for water heating using solar thermal collectors. These activities involve the efforts of the industry, which keep pace with the latest technology in the world, and are in a race to provide the most reliable technological solution to the customer for harnessing solar energy in an economical and robust manner. This has been the backdrop theme of almost all the chapters included in this book, which have been contributed by various authors from across the world. This is the first chapter of the book, and thus provides an overview of the various topics that will be covered in this book, ranging from an energy roadmap for the future, to technologies advances in the field of photovoltaics and solar cells (DSSC—Dye-Sensitized Solar Cells). It also includes details of solar thermal collector, along with the discussion about its heat transfer aspects. Apart from the two primary uses of solar energy—electric power generation and water heating—there are numerous applications for which it has been used over the years. Several such applications are also discussed in some of the subsequent chapters, such as refrigeration, desalination, gasification, and cooking. © 2019, Springer Nature Singapore Pte Ltd.