This brochure is for those who want to know what health is based on. It does not tell a little about everything, but everything - or almost everything - about one link - about the kidneys. The technology of their activities, on which the well-being of the whole organism depends, and the mechanism of diseases are revealed. The factors of everyday life and habits that do not pass without a trace for the kidneys are named, the methods of examination and the principles of treatment are explained.