Race and ethnicity play a pivotal role in our lives, informing how we see ourselves and the world. Communities built around racial and ethnic identity can offer internal sources of resilience. But these parts of our identity may also have adverse social implications, influencing our chances of receiving quality medical care, getting a job offer or a loan, or being wrongly stopped by the police. Despite the social significance of race, the clusters of common physical characteristics and the labels we use to describe it can change greatly over time. Ethnicity, meanwhile, may correspond with cultural practices such as the foods we enjoy, the languages we speak, and how we worship.