Research into the biological basis of gender identity is in its infancy, but clues are beginning to emerge.

Scientists look to a leaf beetle’s genitals for lessons on improving catheter strength.  

A man who lost his penis due to cancer has received the organ from a deceased donor.

A phallus-less reptile goes through a developmental stage with external genitalia, suggesting a common origin for the organ among amniotes.

This year marks the 150th anniversary of an autopsy report describing the first known case of a sexual development disorder.

The genitalia of mammals and reptiles develop from two different tissues, but the structures share common genetic programs and molecular induction signals.

Not to be outdone by vertebrates, invertebrates employ a suite of interesting structures and behaviors to accomplish procreation.