Okay kiddo, so you know how everyone has different parts of their body that make them a boy or a girl, right? Well, some people are born with bodies that don't quite match up with their chromosomes (the special things inside our cells that help make us who we are).
One of these differences is called complete estrogen insensitivity syndrome. This means that someone who has this condition was born with XY chromosomes (like a boy), but their body doesn't respond to the hormone called estrogen (which is more common in girls).
That means even though their body is physically male, they won't grow the usual male parts like the penis and testes. Instead, their body will look more like a female's, with things like breasts and a vagina.
This condition can be diagnosed at birth or later in life. Some people with complete estrogen insensitivity syndrome may find out when they go to see a doctor because they have never started their menstrual cycle (the time when girls start to bleed from their vagina each month). In some cases, the condition may not be discovered because people with it look and feel fine.
It's important to remember that everyone is different and unique in their own way, and it's okay if someone's body doesn't look like what we expect. All bodies are special and deserve love and respect.