but as ali rogin reports, even with improvements over the last 30 years, women's sexual health remainsrstudied. >> just about half the world's population has one. in the medical world, it's been discovered, forgotten, and declared rediscovered, but is usually dismissed as an afterthought. and often, it's been seen as shameful. the clitoris is considered the only organ that exists solely for sexual pleasure, but it's also a crucial part of female anatomy. just as sexual health is critical to overall well-being. so why is the clitoris and the sexual health of people who have them still so understudied? joining me to discuss are urologist and sexual health expert dr. rachel rubin and rachel gross, a science journalist and the author of the book "vagina obscura." rachel gross, i'm going to start with you. why do we, and when i say we, i mean doctors, academics, and the general public, why do we know so little about the clitoris? >> i think, as you said, there is a long history behind this. in general, we know far less about female bodies than male ones, and that's partially because of who'