Over the last several decades, several factors have contributed to a major transformation in heat pipe science and technology applications. The first major contribution was the development and advances of new heat pipes, such as loop heat pipes (LHPs), micro and miniature heat pipes, and pulsating heat pipes (PHPs). In addition, there are now many commercial applications that have helped contribute to the recent interest in heat pipes. For example, several million heat pipes are manufactured each month for applications in CPU cooling and laptop computers. Numerical modeling, analysis, and experimental simulation of heat pipes have significantly progressed due to a much greater understanding of various physical phenomena in heat pipes as well as advances in computational and experimental methodologies. A review is presented hereafter concerning the types of heat pipes, heat pipe analysis, and simulations.