Biophysicist Raguvire Partasarati explains that four physical principles determine the structure and behavior of biological systems. These principles include self-assembly, regulatory networks, predictable randomness, and scaling. They underpin the diversity of living nature and make it possible to develop biotechnologies. Partasarati offers a wealth of examples to show how these physical principles work, including the packaging of viral DNA, the arrangement of membranes, setting up a body plan during embryogenesis, organs on a chip, genome editing, prion diseases, and cystic fibrosis.