The development of all available medical laser systems is based on physical hypothesis and experiments. Already in 1917 Einstein hypothesized that accelerated electrons produce electromagnetic beams of a certain wavelength. In the following years, his theories were confirmed in experimental studies. Yet, not until 1960 did Maiman, a young American physicist, construct the first laser device, a ruby laser, which emitted visible light at a wavelength of 694.3 nm. In 1960 and 1961, Goldmann and Campbell used a ruby laser for dermatological and ophthalmologic treatment. However, it had taken many years until the laser became widely accepted for various medical applications. Alongside high-powered lasers that are used in surgery, low-level HeNe lasers and GaAs lasers have also been developed.