treatments for obesity. 1923. Straddling the nineteenth and twentieth centuries developed three conceptions or medical paradigms: the anatomical (the origin of the disease is in the “injury”), the pathophysiological (searching for the origin in the ‘process’ altered) and etiologic ( or external causes), all heirs to the scientific model, mainly biologist. Whenever individual genius springs forth less overall impact and research based on interdisciplinary teams or dedicated to very specific searches. The twentieth century is the century of evidence-based medicine: the standard protocols of action, backed by scientific studies, being replaced with the views and personal experiences of each doctor, and get to give the body of knowledge physicians a global validity in an increasingly interconnected world.Among the most prominent physicians of this century include Sigmund Freud, the great revolutionary of psychiatry, Robert Koch discovered the bacillus that causes tuberculosis, Paul Ehrlich, the father of immunology, Harvey Williams Cushing, father of neurosurgery, or Alexander Fleming, discoverer of penicillin, which starts with the “antibiotic era” of medicine. In 1948 WHO was founded under the aegis of the UN, the first international medical organization specialized in managing policies for prevention, health promotion and intervention worldwide. And in this dense network of research teams and is developing overspecialized also a new way of understanding the disease, or rather, the sick, the thread of an awakening society environmentalism (understood as a social movement that aims to integrate the individual back the environment).The seventeenth to nineteenth centuries, deeply rationalist, endeavored to classify the organs, tissues and diseases and to establish the rules for the functioning of physiological and pathological processes. But the evidence of the complexity of human beings leads to the conclusion that no diseases but sick people. In this context develop models of health and disease proposed by the World Health Organization, and which incorporate psychological and social spheres to the biological determinants of health as people. In 1978 we celebrate the International Conference on Primary Health Care in Alma-Ata, which shows that statement, and the crucial importance of social measures (adequate supply of drinking water and food, vaccinations …) and primary health care level to improve the health of populations.The motto (ultimately unfulfilled) of this conference was Health for All by the year 2000. The technical medicine, capable of unlocking the secrets of the human body through devices such as MRI, has generated a social current “medicalized” in which problems and behaviors become diseases. This will achieve two objectives: to transfer the responsibility of the individual to “illness”, and leave the solution in the hands of the technique. However, in parallel with that evidence, the development of pharmacology at the industrial and economic has made the twentieth century medicine in the drug tax as an icon of health. Aspirin is synthesized by Felix Hoffmann in 1897 has become a symbol of the culture of this century.These contradictory features (a dehumanized medicine and commodified, but that has eradicated diseases like smallpox and polio and has successfully increased the average life expectancy over 70 years in most developed countries) are the synthesis of modern medicine. From Emil Kraepelin and Eugen Bleuler, Sigmund Freud and later, off one of the later branches of modern medicine: psychiatry. The first is the pioneer in proposing that psychiatric disorders are mainly caused by biological or genetic disorders. Bleuler made some fundamental contributions in clinical psychiatry (he should be the terms of schizophrenia and autism) and can say that Freud is the founder of the psychoanalytic movement.The psychoanalytic school, renewed by his disciples, has followed more or less force after the death of its founder and main ideas have transcended to psychiatry reached such disparate disciplines as art, religion, or anthropology becoming part general culture. Subsequently psychiatry collected through Karl Jaspers, the influences of phenomenology and existentialism and by John B. Watson, behaviorism. In the last decades of the twentieth century psychiatry developed a psychopharmacological school based on the premise that the mechanism of action of psychoactive drugs in turn revealed the pathophysiological mechanism secondary to psychiatric disorder thus approaching the neurophysiology.More technical achievements are worth mentioning are the blood transfusion carried out successfully for the first time in this century through the work on developing blood groups by Karl Landsteiner, or transplantation of organs, flag, not the first, but by the most successful media and its developers: Christiaan Barnard, first surgeon to successfully perform a heart transplant.