Medical Lasers affect human tissue by transferring radiant energy to the target cells. The radiant energy turns into heat when the cells absorb it. As the target cells are heated, all their proteins are destroyed and their internal pressure rises rapidly. The cells then explode, giving off smoke-like steam called a laser plume. The major effects of most lasers on tissue are coagulation of blood and protein, and vaporization. Vaporization is the removal of tissue through its conversion from a solid to a gas.In general, there are two types of medical laser systems, contact and non-contact. Contact systems work by sending laser light through a fiber or sapphire crystal tip. The tip absorbs the radiant energy and becomes hot. Direct contact between the tissue and the heated tip causes conduction of the heat energy from the tip to the tissue, resulting in the vaporization of the target cells. In contrast, non-contact laser systems do not directly touch the tissue. Instead, the laser light transfers radiant energy to the tissue. Heat results when the cell absorbs the radiant energy and the molecules in the tissue begin to move. In both types of system, the laser light itself is not hot. Heat is created only after the laser's radiant energy is absorbed, either by the tip or by the tissue.