Why do onions make my eyes water?
Onions contain a mildly stimulating oil. This oil readily forms a vapor (gas) which escapes when the onion is cut. It not only gives the onion its sharp odor, but also irritates the eye. The eye reacts by producing a flow of tears to wash away the pungent stuff the onion gives off.
When you boil an onion you drive off most of its strong oil.
The onion is an interesting vegetable. The onions you eat are bulbs, or rounded buds of an underground stem from which new onion plants can grow.
The onion has a brownish, papery covering. Inside are many tightly arranged white leaf layers which contain food for the growing plant.
Onion plants also form seeds from which new onion plants can grow. Many other plants like tulips, daffodils, and hyacinths, also grow from bulbs. – Dick Rogers