Sexual stimulation is any stimulus (including bodily contact) that leads to, enhances and maintains sexual arousal, and may lead to orgasm. Although sexual arousal may arise without physical stimulation, achieving orgasm usually requires physical sexual stimulation. Sexual stimulation is any stimulus (including bodily contact) that leads to, enhances and maintains sexual arousal, and may lead to orgasm. Although sexual arousal may arise without physical stimulation, achieving orgasm usually requires physical sexual stimulation. The term sexual stimulation often implies stimulation of the genitals, but may also include stimulation of other areas of the body, stimulation of the senses (such as sight or hearing) and mental stimulation (i.e. from reading or fantasizing). Sufficient stimulation of the penis in males and the clitoris in females usually results in an orgasm. Stimulation can be by self (e.g., masturbation) or by a sexual partner (sexual intercourse or other sexual activity), by use of objects or tools, or by some combination of these methods. Some people practice orgasm control, whereby a person or their sexual partner controls the level of sexual stimulation to delay orgasm, and to prolong the sexual experience leading up to orgasm. Physical sexual stimulation usually consists of touching the genitals or other erogenous zones. Masturbation, erotic massage, sexual intercourse, a handjob or fingering are types of physical sexual stimulation involving the genitals. Sexual arousal is usually triggered through sensitive nerves in these body parts, which cause the release of pleasure-causing chemicals (endorphins) that act as mental rewards to pursue such stimulation. A person may also become sexually aroused by touching another person's genitals or other body parts. The bulbocavernosus reflex is triggered by stimulation of the glans penis or clitoris. The purpose of sex toys is to provide pleasure and stimulation through an alternative route than just using people's bodies. They can be used by someone on their own, with partnered sex, or group sex. They can be exciting and provide new types of stimulation that the body cannot produce, such as vibrations. Sex toys have been used as a source of sexual stimulation for thousands of years. There have been dildos found from the Palaeolithic era, made of Siltstone and polished to a high gloss. Dildos were also made of camel dung and coated with resin. Historians are uncertain whether these have been used for religious rituals or for personal pleasure. It is known that dildos were used for fertility rituals, however. The Ancient Greeks created their dildos from a carved penis covered in leather or animal intestines to create a more natural feel. The Romans created double-ended dildos for use with a partner. Ancient Chinese dildos were made of bronze or other metals and some were hollow allowing them to be filled with liquid to simulate an ejaculation. These were used because wealthy Chinese men would often have too many wives to please. In Persia, they thought that the blood of the hymen was unclean, and should be avoided by husbands. On the night before a lady's wedding, a local holy-man would come and break her hymen with a large stone dildo, a ritual also used to confirm the virginity of the bride.