This common chronic condition — where tissue similar to what grows inside the uterus grows elsewhere in the body — is barely understood. So why is a condition so prevalent and painful still so unknown? It has a lot to do with who gets to ask research questions. Correction, August 18: An earlier version of this episode implied that the tissue involved in endometriosis is the same as the endometrium, which lines the uterus. It is similar tissue, but not identical. For more, go to http://vox.com/unexplainable It’s a great place to sign up for our newsletter, view show transcripts, and read more about the topics on our show. Also, email us! unexplainable@vox.com We read every email. Support Unexplainable by making a financial contribution to bit.ly/givepodcasts Learn more about your ad choices. Visit podcastchoices.com/adchoices