This volume includes twelve novel empirical papers focusing on the behaviour and cognition of both captive and wild bonobos (Pan paniscus). As our species less known closest relative, the bonobo has gone from being little studied to increasingly popular as a species of focus over the past decade. Overall this volume demonstrates how anyone interested in understanding humans or chimpanzees must also know bonobos. Bonobos are not only equal to chimpanzees as our relatives, but they are also unique.