This article is the seventh in a series on the biological basis of child health. It describes early developmental milestones, stages of growth, puberty and the development of the reproductive system. It also outlines the methods used to assess growth and development, and describes conditions that affect growth and development in infants, children and young people. Understanding childhood growth and development is crucial for children’s nurses, who need to be able to identify potential deviations from the norm, since these often reveal underlying conditions that require treatment.