In this episode, the first of the extraordinary BBC series A Perfect Planet: The Ocean. Alberto Angela will be at the National Archaeological Museum in Naples to tell us who the gladiators were. A brand new knee! A clever blend of nanomaterials and stem cells promises to free us from osteoarthritis. An ecological transition is a huge process of change that contains other changes within it, each of which contains yet more. The energy transition, for example, is part of the ecological transition, but it is itself made up of transitions in energy consumption in transportation, homes, and factories. One strategy for avoiding the use of pesticides is biological control, that is, exploiting the very weapons that Nature provides, and therefore using their natural predators—other insects, aphids, or small worms called nematodes—against parasites.