An outstanding Canadian doctor, biologist and endocrinologist of Austro-Hungarian origin, the founder of the theory of stress and the developer of the concept of the general adaptation syndrome. He described stress as a physiological and psychological reaction of the body to any demands placed on it, distinguishing three stages of stress: anxiety, resistance and exhaustion. Selye introduced the concepts of negative stress (distress) and positive stress (eustress), viewing stress as an adaptive process important for survival. His scientific work had a huge impact on medicine and psychology, and he himself is considered one of the most productive scientists of the 20th century in this field.