Cryonics (from Greek kryos, which means 'cold') is the process of vitrifying a human (or animal) about −196 degrees Celsius (−321 degrees Fahrenheit; 77 kelvins) after a doctor says they are dead. People do that in hope that, in the future when medicine becomes better, they can have life again, solve their health problems and have eternal life.
Cold people like this are not awake at all as they have no brain activity. The law also says they are dead. Their body and its brain are made more like glass than ice because ice would harm their cells more. To do this, their blood is replaced with chemicals called cryoprotectants, which act like anti-freeze (stops to freeze).
There are four big cryonics companies: