This study examines the sexual development of transmasculine adolescents undergoing testosterone-based gender-affirming hormone therapy. It uses a clinical sample from the Center of Expertise on Gender Dysphoria at Amsterdam UMC. The study focuses on three key questions. The first asks about the sexual and romantic experiences of these adolescents during testosterone therapy. The second question asks what the changes are after starting gender affirming hormone therapy.  The third and final question asks if there is an association between puberty suppression and body image influencing sexual development.