In the summer of 2015, shortly after Caitlyn Jenner came out as transgender, the NAACP official and political activist Rachel Dolezal was outed by her parents as white, touching off a heated debate in the media about the fluidity of gender and race. If Jenner could legitimately identify as a woman, could Dolezal legitimately identify as black? Taking the controversial pairing of transgender and transracial as his starting point, Rogers Brubaker shows how gender and race, long understood as stable, inborn, and unambiguous, have in the past few decades opened up--in different ways and to different degrees--to the forces of change and choice. Transgender identities have moved from the margins to the mainstream with dizzying speed, and ethnoracial boundaries have blurred. Paradoxically, while sex has a much deeper biological basis than race, choosing or changing one's sex or gender is more widely accepted than choosing or changing one's race. Yet while few accepted Dolezal's claim to be black, racial identities are becoming more fluid as ancestry--increasingly understood as mixed--loses its authority over identity, and as race and ethnicity, like gender, come to be understood as something we do, not just something we have. By rethinking race and ethnicity through the multifaceted lens of the transgender experience--encompassing not just a movement from one category to another but positions between and beyond existing categories--Brubaker underscores the malleability, contingency, and arbitrariness of racial categories. At a critical time when gender and race are being reimagined and reconstructed, Trans explores fruitful new paths for thinking about identity.