Auxology is the science of how humans grow: it tracks changes in height, weight, and body proportions from conception through adolescence. Auxologists establish the growth standards and charts that pediatricians use to judge whether a child is thriving, and they investigate how nutrition, disease, socioeconomic conditions, and genetics shape growth patterns across populations. The field revealed phenomena such as the secular trend of increasing height with improving nutrition and the critical windows when undernutrition permanently stunts growth. Its methods, precise measurement compared against reference populations, underpin global nutrition surveillance, from village health posts to international surveys. Auxology turns the simple act of measuring a child into one of public health’s most powerful diagnostic tools.