It is a paradox that while race is a central reality in the U.S., it is in a fundamental sense an "illusion." Contrary to much popular belief, racial groups are social constructions without any biological or scientific basis. Yet beliefs about race lead people to classify and label people in certain ways, and this in turn affects their identities and behavior.

Although race has been discredited as a scientific concept, it remains an important popular belief throughout much of the world, and as such, an important subject of sociological study. Please discuss how systems of racial classification have changed over time, how they become embodied in institutional practices, and how they remain points of contention.