The present book discusses the Nobel Prizes in physiology or medicine from 1969 to 1971. The 1969 prize recognized Max Delbrück, Alfred Hershey and Salvador Luria. Their pioneering studies of viruses infecting bacteria, bacteriophages, from the mid-1940s through the 1950s laid the foundation for the wide field of molecular biology. The nature of the gene was finally understood. Insights into the biochemistry of the critical information molecules, the nucleic acids, opened wide vistas for interpreting their expression and the interaction of their product with other gene products.The contact between the endings of a nerve and a target cell, the synapse, has always stirred the imagination of scientists. A number of the insights gained have been highlighted by Nobel Prizes in physiology or medicine. In 1970 the prize recognized Bernard Katz, Ulf von Euler and Julius Axelrod. They had revealed how signaling substances in the nerve terminals were stored in packages, released by membrane fusion and inactivated or reused by particular metabolic events.The recipient of the 1971 Nobel Prize in physiology or medicine was a single scientist, Earl Sutherland. He had identified critical molecules in cells that allow signals elicited at their surface via a number of internal steps to influence the expression of specific genes in the nucleus. The new kind of information transmitting molecules were referred to as "secondary messengers". They represent a critical part of a highly complex network of signaling controlling the operative conditions of the cell by adjustments of the so-called intermediary metabolism.The widening insights into functions of specialized cells and their complex interactions have led to the development of many kinds of remedies.