VICE on HBO's latest episode explores the rigors and possibilities of fecal medicine.

Intestinal infections are, well, undesirable to say the least. Vomiting, diarrhea, and indigestion are all part of the package, and the worst part is that some of the more severe types are capable of outfighting any medicine intended to cure them. In cases like this, the infection can escalate from debilitating to fatal. That’s why science has turned to an unlikely candidate for help — poop.

Fecal transplants, where doctors put feces from a healthy donor in an infected patient’s gut, are designed to help replenish life-saving microbes that have been overtaken by bad bacteria. The Washington Post once called the procedure “the most successful effort to hack the microbes that live in and around us (known as our microbiome or microbiota) to date.”

But what does it take to be a poop donor, and what’s in it for you?

Turns out, the process is a lot more selective than you’d think. Only about 3 percent of donor applicants are actually selected, and then they have to abide by strict diet and health rules to continue donating their waste. They complete a 109-question quiz about their medical history and daily activity, then undergo blood testing to make sure there’s nothing offensive in their systems, like HIV — or Pepsi. Only after passing all the tests will donors be paid about 40 dollars for each … sample.

Check out the video to see the inside of a lab dealing with fecal transplants.