At the most basic level, the experience of sexuality begins with an individual’s genotype and phenotype. From this basic biologic underpinning, children develop a gender identity during early childhood. Eventually, each individ-ual develops a sense of self as a sexual being and a sexual orientation. Each of these latter components is fluid and can vary over time and with particular circumstances. For example, many individuals who consider themselves het-erosexual periodically engage in sexual encounters with same-sex partners.