Critical care medicine developed out of other subspecialties' need to provide care for their most critically ill patients. Advanced technologies, the understanding of the pathophysiology of critical illness, and the development of the multidisciplinary team have made this care possible. Pediatric critical care medicine emerged in the 1960s and has expanded dramatically since then. The field has made major advances in the areas of lung injury, sepsis, traumatic brain injury, and postoperative care. We review here the evolution of modern pediatric critical care medicine from its roots in general pediatric and cardiac surgery, adult respiratory care medicine, neonatology, and pediatric anesthesiology to its current state as a unique discipline.