why do tears come when we cut onions??

Onions are made up of a tunic of outer leaves (the brown layer), scales (the white firm juicy edible part), and the basal plate (often called the "hairy part" or the "root"). Tears come when we cut onions because: 1. When you cut the basal plate or shoot, they release an enzyme. 2. That enzyme reacts in the rest of the onion to release a gas. 3. When that gas combines with water, it creates an acid. 4. If that water is in your eye, you have acid in your eye. That makes you cry.