Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com. Why do we sneeze? – Naomi, 9, San Francisco, ...

Add Yahoo as a preferred source to see more of our stories on Google. Aaaaa-choo! While your first thought may be to say "Gesundheit!" your second might be to ask: "Where did that sneeze come from?" ...