Carbon nanotubes (CNTs) are cylindrical nanostructures composed of carbon atoms arranged in a hexagonal lattice. They can be either single-walled or multi-walled, with diameters ranging from less than 1 nanometer to several nanometers and lengths up to several centimeters. Their unique properties include exceptional strength, flexibility, and thermal and electrical conductivity. These characteristics make them valuable in various applications, from strengthening composite materials and enhancing battery performance to enabling advances in electronics and nanomedicine. CNTs also play a critical role in developing new materials with tailored properties, such as conductive films, sensors, and nanorobots. This book discusses the fundamentals as well as modern applications of carbon nanotubes. It is a compilation of chapters that discuss the most vital concepts and emerging trends in the field of carbon nanotubes. Through this book, we attempt to further enlighten the readers about the new concepts in this field.