Only twenty-five years ago, the first evidence of self-medicating behaviour among animals was reported among chimpanzees. On the basis of this pioneering research, led by the American Michael Huffman, a new science was founded: "zoopharmacognosy", or the study of animal pharmacopeia. Animals are apparently able to treat themselves actively, to detect natural substances that can provide a remedy for health problems, or to prevent them. The primatologist Michael Huffman explains how he discovered that chimpanzees can heal their diseases with medicinal plants from their environment. The scientist then comments on other very surprising examples: Birds that disinfect their nests by filling them with aromatic plants with repellent properties, a rodent that covers its coat with toxic sap as a poisonous defence against predators and elephants that place mud plasters on their injuries. Some therapeutic behaviours may even be transmitted socially among certain species.