Cryonics is the low-temperature preservation of the brain and body on death, so as to preserve the tissue structures that hold the data of the mind. This offers a chance of future restoration to life via advanced medical technologies, which is more than can be said for the other post-mortem options presently available to us. Here is an interview with Max More of the Alcor Life Extension Foundation, one of the two long-established cryonics providers in the US:
Somebody might opt to be placed into biostasis at the end of their natural life [for] the same reason that a person might choose to have open heart surgery or an experimental cancer treatment. Essentially, we see cryonics as an extension of critical care medicine. If you were unlucky enough to go into cardiac arrest whilst walking down the street 50 years ago, you would probably have been pronounced dead at the scene. Nowadays, paramedics routinely use defibrillators and cardiopulmonary resuscitation (CPR) to revive patients who would simply have died in the past.
Cryonicists recognise that what we call 'dead' is somewhat arbitrary; it depends largely on the level of medical technology that is available at a particular point in time. When today's doctors declare a person clinically dead, they are not saying that that person is biologically dead. They are not saying that all of their brain cells have exploded or disappeared. They are simply stating that the person in question has become non-functional in a way that they are unable, or unwilling, to fix. So, why give up on that person? They're still potentially there; their brain is intact. As cryonicists, we are looking towards the future. We can do things today that weren't possible 50 years ago. It's clearly going to be the case that in 50 years' time, we will be capable of achieving things that are not possible today. In the future, we will be able to fix many things that we cannot fix at present. Hopefully, this will include the ageing process itself.
If you look deeper into cryonics, you will begin to recognise how it is connected to other sciences. Organ donation, for example, is a current research area that shares several commonalities with cryonics. The initial procedures that we conduct in order to maintain biological viability are much the same as those carried out when preserving a donor organ. Moreover, there is plenty of evidence to suggest that what we are doing is working. Electron microscope studies have demonstrated that when we place a person into biostasis, the connections between their brain cells persist. Given what we know about human memory, this indicates that the person is still potentially there.
Cryonics is beginning to make sense within the context of medical advances that are taking place across a range of sectors. People are putting the pieces together and arriving at their own conclusions. Nobody knows whether or not cryonics will ultimately succeed, but it certainly isn't crazy. In fact, it looks a whole lot more plausible today than it did in the past.