"Bless you"

whenever someone sneezes, you say "bless you" or hear someone else say these words. 

the words are spoken to wish someone good health and a long life.The phrase "God bless you" is attributed to Pope Gregory the Great, who uttered it in the sixth century during a bubonic 

plague epidemic (sneezing is an obvious symptom of one form of the plague). It entered the English language in the early part of the 20th century, brought to the United States by German-speaking immigrants.

People all over the place believe differently about what happens while sneezing. Some people believe that the soul comes out when you sneeze, some others believe that the devil might come in, others think that the heart will stop with a sneeze and thats why they wish them a long life.