Yep — we’re talking about the mystery fluid that shoots out of some women during orgasm or stimulation. Maybe you’ve seen it in porn, squirted yourself, read about it online, listened to your friend brag about her fountain-like abilities, or wondered if it’s actually legit or just pee.

We’ve known about squirting since the fourth century, where it’s mentioned in several ancient Chinese Taoist texts. Aristotle, an ancient Greek scientist and philosopher, described the emission of female fluids in his medical writings around 300 B.C. These days, doctors remain interested in squirting and are conducting clinical experiments to learn more about it. Is it the same biological response as male ejaculation? And, um, what exactly… gets squirted — is it pee, or something else entirely? Does it come out of the vagina or the bladder?

The intrigue surrounding squirting is definitely not limited to clinicians. Maybe you’ve personally experienced it or have always been curious how it happens. We turned to science to answer your — and our — most pressing questions.

Let’s talk vocab: ‘squirting’ vs. ‘female ejaculation’

While the terms “squirting” and “female ejaculation” are often used interchangeably, research shows these physiological responses and the substances they produce are different.

In this 2011 study, researchers performed biochemical analysis on two distinct female fluids expelled during sex. The “clear and abundant” fluid ejected in gushes was described as being similar to diluted urine. The second liquid was found to be comparable to components of male semen and released in smaller quantities compared to the other. The authors concluded, “The real female ejaculation is the release of a very scanty, thick, and whitish fluid from the female prostate, while squirting is the expulsion of a diluted fluid from the urinary bladder.”

Dr. Madeleine Castellanos, tells BuzzFeed, “Since it’s such a tiny amount and some gets pushed back into the vagina, you may not notice [female ejaculate].”

Squirting for science
In 2014, scientists decided to take their studies of squirting and female ejaculation a step further by performing a biochemical analysis of the fluids emitted (similar to the 2011 study) and pelvic ultrasound scans to observe the bladder. Seven women reporting “massive fluid emission” during sexual stimulation participated in the study.

First, the researchers asked the women to empty their bladders, provide a urine sample, and then undergo a pelvic ultrasound. The second part of the study required the women to become sexually aroused in an examination room, either alone or with a partner. As the women neared orgasm, they were asked to undergo another ultrasound. (Sounds like a turn on, right?) After this second ultrasound, the women resumed sexual stimulation in the exam room. After eventually orgasming and squirting, the researchers requested another urine sample and performed yet another ultrasound. They also collected the squirting sample.

Here’s what they discovered: the first ultrasound confirmed the women’s bladders were empty after using the bathroom before arousal. But the researchers observed a noticeable filling of the women’s bladders from the ultrasound taken right before squirting. After squirting, the third and final ultrasound revealed women’s bladders appeared to be empty once again. This suggested the squirting samples were urine.

When the researchers compared the chemical makeup of the urine and squirting samples, they discovered that they closely resembled each other. (The researchers did not observe the presence of female ejaculate in any of the squirting and post-squirting samples from five out of seven of the women. However, it was present in samples for two participants.)

The authors wrote, “The present data based on ultrasonographic bladder monitoring and biochemical analyses indicate that squirting is essentially the involuntary emission of urine during sexual activity, although a marginal contribution of prostatic secretions to the emitted fluid often exists.” This means the researchers believe that squirting is primarily just pee, though there may be a small amount of fluid from from the female prostate in the liquid, too.

So, if you squirt, what’s on your sheets? According to science, probably just pee. There’s a chance, however, that some female ejaculate may also be present. Thanks to research, we also know that that vaginal squirting is a thing and that it’s quite different from female ejaculation, in terms of how much is produced and where the fluid comes from. (There you have it, Aristotle.)

English Taylor is a San Francisco-based women’s health and wellness writer and birth doula. Her work has been featured in The Atlantic, Healthline, Refinery29, NYLON, and Modern Fertility. Follow English and her work at https://medium.com/@englishtaylor or on Instagram at @englishtaylor.