The rate of introduction of new products and technologies is steadily rising. At the same time, pressures to reduce time-to-market are mounting. Only companies that are able to realize products rapidly are able to survive today. From a technological viewpoint, rapid product realization involves rapid design, rapid prototyping, and rapid tooling. Fortunately, a class of technologies collectively called rapid prototyping (RP) technologies, has emerged in the last two decades to meet these requirements. This text provides an updated overview of rapid prototyping (RP) technologies at a level of detail suitable for university engineering students taking courses on RP as well R&D and operating professionals from industry interested in RP. While the emphasis is on laser-based technologies, other processes are also discussed. Each important RP process, the part/assembly modeling techniques, the materials used, process itself, advantages and disadvantages, accuracy and finish issues as well as application potential are discussed.