Cryogenic and Cryonics are two different things. Options 1 and 2 are related to cryogenics. Option 3 describes cryonics . Future revival in Cryonics is done because it is believed humans and animals can be kept alive until in the future a medicine discovery cures them. A central premise of cryonics is that long-term memory, personality, and identity are stored in durable cell structures and patterns within the brain that do not require continuous brain activity to survive. The central premises of Cryonics are: Life can be stopped and restarted if its basic structure is preserved. For e.g. Human embryos are routinely preserved for years at temperatures that completely stop the chemistry of life. Vitrification (not freezing) can preserve biological structure very well. For e.g. Adding high concentrations of chemicals called cryoprotectants to cells permits tissue to be cooled to very low temperatures with little or no ice formation. Methods for repairing structure at the molecular level can now be foreseen . For e.g. the emerging science of nanotechnology will eventually lead to devices capable of extensive tissue repair and regeneration (to correct the damages caused due to vitrification).