Sneezing, also called sternutation, is your body's way of getting something irritating out of your nose.
When the inside of your nose gets a tickle, a message is sent to the part of your brain called the sneeze centre.
The sneeze centre sends a message to all the muscles that have to work together to create the sneeze.
Those include the abdominal muscles, chest muscles, diaphragm, the muscles that control your vocal cords, muscles in the back of your throat, and your eyelid muscles.
It's impossible to keep your eyes open when you sneeze.
The sneeze centre makes all these muscles work in just the right order, to send that irritating particle out of your nose - at speeds up to 100 mph.
About one of every three people sneezes when exposed to bright light; they are called photic sneezers. If you are a photic sneezer, you got it from one of your parents, since it is an inherited trait.
Watch: a sneeze explained in slow motion. Source: YouTube
Source: Nemours Center for Children's Health Media