Femtosecond technology, with its ultrashort light pulses, forms an innovative laser technology that can be used for numerous technical applications. This monograph gives a comprehensive overview of the principles and applications of femtosecond lasers, especially as applied to medicine and to production technology. The principles and features of such femtosecond technology are described, and the lasers, systems and technologies that are required in these potential fields of application are investigated. The advantages and problems of ultrashort laser pulses are discussed in more detail in the context of applications in the micro-machining of technical materials such as drilling, surface structuring and cutting; in medical use such as dental, ophthalmologic, neurological and otolaryngological applications; in metrology; and in the generation of x-rays. Safety aspects are also considered.