Will we ever get tired of talking about sex? We sure think about it a lot. We watch people do it a lot on tv and in the movies. We buy all kinds of products and services in the hopes we'll be having sex a lot. And all the magazines tell us we SHOULD be having sex a lot. But that doesn't mean we actually know much about it. Remember, thinking about something doesn't make you an expert! But to help you on your way, we present 25 things you most likely didn't know about sex.

Researchers at the University of Wisconsin-Madison report recently reported that sildenafil (the chemical name for Viagra) increases the amount of oxytocin released by stimulation of the posterior pituitary gland, the small organ under the brain that regulates hormone levels in response to neural signals. The finding is the first indication that erectile dysfunction drugs like Viagra may have physical effects besides increasing blood flow to sexual organs, according to Meyer Jackson, a physiology professor at the UW-Madison School of Medicine and Public Health and author of the study.

Sometimes called the "love hormone" or "cuddle chemical," oxytocin plays several important roles in social interactions and reproduction, including triggering uterine contractions and lactation in women. But it is also released during orgasm and has been linked to sexual arousal in both sexes. Animals and people with high levels of oxytocin are calmer, more relaxed, more social and less anxious.

2. Both the eyeballs and the vagina are "self-cleaning" organs. Kind of like my oven. But not really.

3. Oral sex is ancient history.

According to historians, oral sex has been around since the beginning of sex. "It's prehistory," said Jim Petersen, author of Playboy's "History of the Sexual Revolution" series. "You can find oral sex in almost every ancient culture from Egyptian paintings to stone carvings in Indian temple walls." But there have always been interesting attitudes about it.

In pre-Christian ancient Rome, sexual acts were also expressions of submission and control, as is apparent in the two Latin words for the act: irrumare (to penetrate orally), and fellare (to be penetrated orally). In this ancient culture, it was considered to be abhorrent for a male to be in any way penetrated (or in other words, controlled) by another person of lower social standing during sex.

If your lover ever tells you his penis is so hard he feels it might burst, take heed. According to a news story on a British website, the penis of a 28-year-old Romanian man actually exploded while he was making love to his girlfriend.

The young man, Ilarie Coroiu was taken to hospital in the Transylvanian town of Cluj after his girlfriend, Magdalena, 18, "felt something strange" and noticed that the bed was covered in blood.

Dr Angela Domocos, head of the accident and emergency department at Cluj General Hospital, said: "It is very rare for this to happen. We call it an exploded penis because it happens when the blood cavities in the penis burst."

5. Women have record orgasms (when they have them).

The most recorded orgasms in one hour is 134 for a woman, and 16 for a man. The longest recorded female orgasm is 43 seconds, with 25 consecutive contractions.

6. Kegel exercises do more than control your bladder.

Pompoir (also known as "playing the flute") is the practice of stimulating the man's penis solely through use of the woman's vaginal muscles. Both partners remain still, and the woman strokes the man's erection by rhythmic, rippling pulses of the PC or pubococcygeus muscles. If you want to get good at pompoir(ing?) practice those Kegel exercises.

A man's "G" Spot should actually be called the "P" spot, because his magical male part is the prostrate gland. Nestled in his pubic bone and surrounded by the pelvic muscles, the prostate gland responds to pressure applied either inside the rectum or from outside in the space between the scrotum and rectum. When the prostate is stimulated, it can intensify your man's orgasm significantly. In fact, some men are able to achieve orgasm from this stimulation alone.

8. Columbus discovered the clitoris.

That would be Renaldus Columbus of Padua, who in 1559 claimed that previous anatomists had overlooked the very existence of 'so pretty a thing'. Columbus was a lecturer in surgery at the University of Padua and in his book De re anatomica described the "seat of woman's delight." He concluded, "since no one has discerned these projections and their workings, if it is permissible to give names to things discovered by me, it should be called the love or sweetness of Venus."

9. Masturbation is good for you.

Every 13 year-old teenage boy will agree with that statement, but it's good for us girls too. Studies show that orgasm can reduce sensitivity to pain, relieve menstrual cramps, and alleviate stress-possibly due to a surge in hormones like oxytocin and dopamine.

From ancient Greece to Freud's time, doctors stimulated orgasms in women via "medical massage" to treat the catchall female ailment known as hysteria. Galen, a prominent physician from the second century, wrote that hysteria was a disease caused by sexual deprivation in particularly passionate women. Hysteria was noted quite often in virgins, nuns, widows and, occasionally, married women. The prescription in medieval and renaissance medicine was intercourse if married, marriage if single, or massage by a midwife as a last recourse. In the late 1800s, various massage devices were developed to efficiently deal with "hysteria." By 1870, a clockwork-driven vibrator was available for physicians. In 1873, the first electromechanical vibrator was used at an asylum in France for the treatment of hysteria.

11. Semen isn't fattening.

If you're not interested in swallowing, you can't use "dieting" as an excuse. A typical ejaculation fills up about one teaspoon, and has only about 5-7 calories. But that doesn't mean it isn't nourishing. According to Go Ask Alice, the sperm in an ejaculation only makes up about 1 percent of semen. So what else are you getting? A healthy mixture of natural ingredients you'd be pleased to find in your "Propel" including fructose sugar, water, ascorbic acid (a.k.a., vitamin C), citric acid, enzymes, protein, phosphate and bicarbonate buffers, and zinc.

12. Condoms were first promoted by an Italian in the 1500's.

Gabriele Falloppio was one of the most important anatomists and physicians of the sixteenth century (and a contemporary of Renaldus Columbus). In his time he was regarded as somewhat of an authority in the field of sexuality. In his treatise on syphilis he advocated the use of condoms, and initiated what may have been the first clinical trial of the device. It was only later that condoms were used as birth control. And on a separate but very related note, your Fallopian tubes (well, maybe not yours exactly) were first described by Falloppio, which now bear his name.

13. The clitoris is more sensitive than the penis.

Although the clitoris appears as a very tiny organ, it is actually very complex and sensitive. Located above the vaginal and urethral openings, it is actually connected to the inner lips of the vagina. The visible tip or glans of the clitoris is indeed just the tip of an iceberg of much more extensive structures of erectile tissue, which form a padding over the pubic bone. These concealed parts are anatomically and functionally linked to the vagina. The whole structure is densely packed with nerve endings, and although there are a similar number in a penis, they are much more concentrated and closer together in the clitoris.

Written about two thousand years ago, the Kama Sutra is widely considered to be the standard work on love in Sanskrit literature. Only one section deals specifically with sex - including the famous 64 positions. Other sections deal with acquiring a wife, the appropriate conduct of the wife - and the chief wife when there are other wives, how to deal with wives of other people, choosing lovers and dealing with courtesans, and how to be attractive to others.

15. Erections start in the brain.

When the brain says "ooh baby," it sends a rather urgent message down the nerve cells to the penis which stimulates a chemical that dilates the vessels that supply blood to the penis. As a result, the central chambers of spongy tissue in the penis fill with blood, which in turn constricts the veins that allow blood to leave the penis, causing the spongy tissue to swell up and make the penis erect. This "excitement phase" may go on for a few minutes or hours, and the longer it goes on, the more intense the orgasm.

16. Lips are the sex organs on your face.

Lip "skin" is primarily mucous membrane, which has fewer and different glands than ordinary skin. Of course, it's not the only mucous membrane on your body. What covers your most sensitive, intimate organs? The same kind of delicate skin. Lip skin is extremely thin and has almost no melanin, the natural pigment in skin that helps screen out the sun's harmful rays. Nor do lips have the same complement of oil and sweat glands. Sweat glands add moisture to skin, but the lips' only source of moisture is saliva from your mouth (or your lover's).

But the largest vagina on earth belongs to the female blue whale with a normal length of 6 to 8 feet.

19. The largest penis in relation to animal size belongs to a duck.

And he's not giving it up. But seriously, a specimen of the Argentine Blue-bill was found with a remarkable 17-inch long penis (compared to the average for this species of 8 inches). The flaccid penis remained coiled inside the body, but fully erect it was twice the size of the bird. It would be like a man having a 12-foot penis. Yowsa.

20. Sex burns about 70-120 calories for a 130 pound woman every hours.

That puts it on par with driving to work, cooking or bartending.

21. There are approximately 100 million acts of intercourse each day.

If you assume that means two people doing it together, that means every single minute of the day, there are about 140,000 people getting their rocks off - or trying very hard.

One kind expands and lengthens when becoming erect (a grower). The other appears big most of the time, but doesn't get much bigger after achieving erection (a shower). An international Men's Health survey reports that 79 percent of men have growers, 21 percent have showers.

23. Only one man in 400 is flexible enough to give himself oral sex.

It's safe to assume that all 400 gave it a try at one time or another.

24. Anal sex was not legal in all 50 states until 2003.
And just in case you're thinking of planning an exotic getaway, according to Avert.org, homosexual sex is illegal in countries like Singapore, Mauritius, Kenya, India and of course, Iran. But you might be surprised to know some Caribbean destinations also prohibit it, including Jamaica, Barbados, Grenada and Trinidad.

People with urolagnia often like to urinate in public, or urinate on, or be urinated on by other people. These activities are often described by the euphemisms "golden showers" or "watersports" (which should not be confused with water sports, i.e tubing and waterskiing). An alleged urophiliac is Latin heart-throb Ricky Martin, who in an interview with Blender magazine, stated that he enjoyed giving "Golden Showers" and "Yellow Rainbows."

Ok, now you can light up a cigarette. Or brush your teeth.