Eugenics is the "applied science or the biosocial movement which advocates the use of practices aimed at improving the genetic composition of a population," usually referring to human populations.
Eugenics was widely popular in the early decades of the 20th century,
but has fallen into disfavor after having become associated with Nazi Germany and with the discovery of molecular evolution. Since the postwar period, both the public and the scientific communities have associated eugenics with Nazi abuses, such as enforced racial hygiene, human experimentation, and the extermination of "undesired" population groups. However, developments in genetic, genomic, and reproductive technologies at the end of the 20th century have raised many new questions and concerns about the meaning of eugenics and its ethical and moral status in the modern era.