What is onion?

An onion is a round vegetable that grows underground, looking like a small, layered ball wrapped in papery skin. It belongs to the allium family, which means it is a cousin to garlic and leeks.

Onions are packed with layers of fleshy, white or purple rings. Think of it like a set of nesting dolls or a tightly wrapped gift. When you peel it, you find smaller and smaller layers inside. These layers store water and nutrients that help the plant survive winter. We eat them because they add a sweet, sharp flavor to soups, stews, and eggs. The flavor changes when cooked: raw onions are spicy and make your eyes water, but slow-cooked onions become soft and sweet, like caramel.

Have you ever cried while chopping onions? That happens because onions release a tiny gas called syn-propanethial-S-oxide. When you cut the layers, this gas floats up to your eyes. Your eyes react by producing tears to wash the gas away. It is a natural defense system, like a plant sneezing. To avoid tears, you can chill the onion before cutting it, which slows the gas release.