Adenoids are small patches of tissue located high up in the throat, behind the nose. They're part of your body's immune system, helping to trap germs that come in through your nose and mouth. You can't see your adenoids in a mirror because they're tucked away where your nasal passages meet your throat.

Along with your tonsils, adenoids work like security guards when you're young, catching bacteria and viruses before they can make you sick. They're largest when you're a young child and typically shrink as you get older. By the time you're a teenager, they've usually gotten much smaller or disappeared entirely because your body has developed other ways to fight infection.

Sometimes adenoids become swollen or infected, which can make breathing through your nose difficult or cause snoring. When this happens repeatedly, a doctor might recommend removing them with a simple surgery. Many children have their adenoids removed without any problems, since other parts of the immune system take over their job. If you've heard someone talk in a stuffed-up, nasal voice even when they don't have a cold, it might be because swollen adenoids are blocking airflow through their nose.