There are lots of ways to watch sex in this world, but here's a unique and illuminating perspective: sex from inside a vagina. Highly informative, yet in no way safe for an open-office floor plan, this clip — narrated by scientists who explain the body's various contractions, secretions, and reactions — has been viewed more than 21 million times.

The couple in the video attached cameras to their bodies — one at her nipple, one inside her vagina, and another attached to his penis. The final result is a video that was made purely for scientific study, showing every moment of their encounter.

The video details sex in the missionary position, providing a visual explanation as to why missionary may be the ideal configuration when a man and a woman are hoping to conceive. It's not exactly sexy, but it's downright fascinating. Viewers get a close-up view as the glans (the head of the penis) enter the woman, stimulating the clitoris and the front vaginal wall. You can see muscular contractions from the vagina, and the experts walk viewers through the bodily reactions in real time. ("The woman's nipple stays erect throughout intercourse." "As the woman approaches orgasm, she may feel her heartbeat in her vagina...")

It all ends with an intimate view of ejaculation.

If you can deal with the "bom chica bom bom" music playing in the background and the experts (with British accents) talking about science facts while you're getting this unusual perspective on coitus, you're bound to learn a little (or a lot) about the world's favorite pastime.

You can watch the video above and decide just how sexy (or unsexy) sex looks from the inside.