Softcore pornography generally contains nudity or partial nudity in sexually suggestive situations, but without explicit sexual activity, sexual penetration or extreme fetishism, while hardcore pornography may contain graphic sexual activity and visible penetration, including unsimulated sex scenes. Explicit sexual activity, such as sexual penetration, may occur within a session, but is not essential. Am Abend , one of the earliest pornographic films that have been collected at the Kinsey Institute for Research in Sex, Gender, and Reproduction, starts with a female masturbation scene. There are many other variations on male masturbation techniques. Sexual scenarios may involve male domination, gay cock female submission, exhibitionism and erotic entertainment. It is also often mixed with other fetishes in practice, such as voyeurism, denial, etc. To tea bag is a slang term for the sexual act of a man placing his scrotum in the mouth of a willing sexual partner for pleasure or onto the face or head of another person. It generally contains nudity or partial nudity in sexually suggestive situations. Female-to-male strap-on pornography became a popular sub-genre in the United States in the early 21st century, with a number of studios producing dedicated series about it. Simultaneous lesbian milfs penetration of the vagina and anus. Other popular implements are canes, riding crops, whips, switches, birches, sneakers, rolled-up newspapers, rulers or martinet. Cum-shot pornography features a collection of male ejaculation scenes. Although interracial pornography theoretically can apply to depictions of sexual activity between performers of any different racial groups, the term is most commonly used for heterosexual sex acts between black and white performers. This type of censoring also extends to comics, video games, and anime made for adults. Regardless of its origin, BDSM is used as a catch-all phrase to include a wide range of activities, forms of interpersonal relationships, and distinct subcultures.