Many inhabitants of our planet do not want to put up with the finitude of life or insurmountable diseases. Therefore, the most optimistic of them either turn to commercial organizations with money, or bequeath their bodies to science at universities and participate in various experimental programs on cryonics, or "freezing.
The calculation is simple: if some serious disease or elementary old age cannot be overcome by modern methods, then we will put our bodies in conditions in which they can be stored as long as necessary until, first, unfreezing technologies become available and, second, technologies for returning to life and successful treatment become available. That is why, after death, people's bodies (or at least their brains) are placed in special chambers that maintain ultra-low temperatures inside them.
But the thing is that "freezing" transforms the liquid of the body cells into ice, which instantly destroys the cell membranes and makes it impossible to successfully "unfreeze" even in theory. Therefore they try to replace water with liquids that do not turn into ice, but this process requires time and therefore, for example, lesions of nerve and brain tissues will in any case be irreversible. Thus, the idea of freezing is the best that exists today in terms of hypothetical, but still significant life extension, but the current level of technology does not allow to implement this idea to the proper extent. But science and technology are developing at a significant pace, and it is possible that a decisive discovery in this area could be made in the next few decades.