Most research has investigated Multiracial and Multicultural populations as separate topics, despite demographic and experiential overlap between these. This Element bridges that divide by reviewing and comparing Multiracial and Multicultural research to date—their origins, theoretical and methodological development, and key findings in socialization, identity negotiation and discrimination—to identify points of synthesis and differentiation to guide future research. It highlights challenges researchers face when studying these populations because such research topics necessitate that one moves beyond previous frameworks and theories to grapple with identity as flexible, malleable, and influenced both by internal factors and external perceptions. The areas of overlap and difference are meaningful and illustrate the social constructive nature of race and culture, which is always in flux and being re-defined. This title is also available as open access on Cambridge Core.