Growth and development are at the core of paediatric practice and are the fundamental factors that make medical work with children different from adult medicine. All paediatricians must have an understanding of the basic science of growth and development and how to measure them. This is fairly straightforward with regard to physical characteristics, but more difficult for mental development. However, it is a skill that must be familiar to children's doctors working in the fields of neurological disease and mental health and, arguably, to all paediatricians.