In this popular science book, through dialogues with an artificial intelligence specialist, a physiologist presents the basic principles of the organism. For the first time, the organism is considered as a community of 220 types of selfish cells. All cells of the body (and there are about 50 trillion of them) compete for common resources. No cell "wants" to work for another, as this requires the expenditure of its limited energy. Nevertheless, the life products of some cell types have proven useful for others. Such causal chains between different types of cells (e.g., neurons and muscle cells, neurons and secretory cells), as a result of which the organism escaped predators or obtained food, were also useful to the organism. Evolution has preserved only those species whose cells had the ability to counteract the "despotism" of the brain and restore optimal metabolism. Man is healthy as long as biochemical and physiological multilevel mechanisms provide a compromise between effector cells and the main organizer of behavioral response - the brain. It is shown how slowly developing diseases of age are associated with disturbances in this compromise.