Understanding the basics of cryobiology to develop improved cryopreservation procedures has been a major challenge to scientists all over the world. During a typical cryopreservation process ice tends to form at different rates. Intracellular ice formation is generally thought to be lethal as it causes injury to cellular membranes and intracellular structures. Conventional slow freezing protocols involve pretreatment of cells with cryoprotective agents (CPAs) in order to remove some water from the cells and to minimize some other harmful effects of freezing. The rate at which permeable CPA diffuses into the cells varies between the cryoprotectants and is also temperature and concentration dependant. Vitrification has become an increasingly accepted method for preserving embryos, oocytes and, recently, even sperm. An ideal vitrification method produces no ice formation and may therefore be an equilibrium method. The benefits of sperm cryopreservation are numerous in human reproductive medicine.