Eugenics is a set of beliefs and practices aimed at improving the genetic quality of a population, often through selective breeding and sterilization. This controversial movement gained popularity in the late 19th and early 20th centuries, using ideas from Darwinism and Social Darwinism to justify efforts to control human reproduction. Eugenics became notably associated with state policies that aimed to eliminate perceived 'undesirable' traits, which tragically culminated in the horrors of the Holocaust.