Urologists in Japan wanted to get to the bottom of a long-held sex debate — when a woman squirts, is the fluid that is released urine, or something else? To find out, they conducted an experiment that involved injecting an indigo-colored liquid into five women’s bladders.

Two of the women were in their 30s, two were in their 40s, and one was in her 50s, and all of them said they had previously squirted in past sexual encounters.

Unlike vaginal lubrication, where a person’s vagina secretes a white and milky fluid when they’re aroused, squirting involves a clear and odorless fluid. Squirting can happen before, during, or after an orgasm and has a geyser-like quality, sex educator Marla Renee Stewart previously told Cosmopolitan.

After the doctors drained excess urine from each woman’s bladder using a urethral catheter, they injected them with 50 milliliters of a blue-dyed saline solution. In another room, women received manual penetration from a male subject the doctors recruited. They instructed the man to use his fingers and penis “in a way to facilitate squirting.”

When each of the five women squirted, the doctors saw blue liquid come out of their genital areas in videos that captured the experiment. Their findings suggest the liquid women produce when they squirt comes, at least in part, from the bladder, the urologists wrote in their August 24 paper published in the International Journal of Urology.

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