If you've ever menstruated, you probably own a pair of "period panties" — aka, the underwear you first reach for when you're bleeding that'll make sure that you don't have to repurpose your cardigan into an apron at some point during the day. Depending on your flow and your preferences, period panties can vary hugely in cut, hue, and thickness from person to person, but for the most part they're full-coverage, comfy, and aren't so expensive that you'll be heartbroken if you've got to trash them.