In human sexuality, a threesome is sexual activity that involves three people at the same time. A female dominant in a master/slave relationship is often termed a Mistress, not to be confused with the colloquial usage of mistress as a kept sexual partner without a similarly formalized power relationship. Films with risqué content commenced to be produced soon after the invention of the motion picture in the 1880s. Sex parties may be organized to enable people to engage in casual sexual activity or for swinging couples or people interested in group sex to meet, but any gathering where sexual activity is anticipated can be called a sex party. Other possibilities are possible, such as a man having sex with two women who are having sex with each other. The term soft crush refers to the more common fetish surrounding videos involving inanimate objects or small invertebrates being crushed, while the term hard crush refers to such videos involving larger animals with vertabrae, and arguably more pain-susceptible animals . Watersports pornography features sexual activities involving urine, such as golden showers. Most soft crush fetishists momsex avoid being placed under the same label as hard crush fetishists, believing that crush films with larger animals give the entire group a bad label. In addition to mainstream pornography, the popularity of facials has led to creation of its own niche market, like video series that specialize in showing the act. Lesbianism has been a theme in erotic art hentai videos since at least the time of ancient Rome, and many regard depictions of lesbianism to be erotic. Saliva pornography involves salivation and saliva. This industry employs thousands of performers along with support and production staff. Tentacle rape or shokushu goukan is found in some horror or hentai titles, with tentacled creatures having sexual intercourse with female characters. Pornography is often referred to as porn and a pornographic work as a porno. Female ejaculation is the expulsion of fluid by the paraurethral ducts through and around the human female urethra during or before an gay fuck orgasm.