Whereas the XVIII and XIX centuries saw the triumph of such sciences as physics and chemistry, the XX century, and its second half in particular, can be called the century of biology. Indeed, fundamental biological laws have been established, the mechanism of antibiotic action uncovered (which helps fungi to fight bacteria), as well as the mechanism of action and the structure of viruses.Cloning has been carried out; the mechanisms of cancers are being decoded at a molecular level; the non-genetic functions of nucleic acids and those of many hormones have been uncovered, as well as the feedback mechanisms regulating the activity of the endocrine system and, thus, the metabolic processes in the body as a whole. The role has been established that the hypothalamus plays in fine-tuning internal processes in response to external stimuli, as have been the functions of the principal parts of the brain that control various body systems. Particularly tremendous progress has been made in the study of immunity, with its principal components deciphered.