An oat is a type of grain that grows in fields, with seeds that form in small clusters at the top of tall, grass-like stalks. When you eat oatmeal for breakfast, you're eating oats that have been hulled (the outer shell removed), steamed, and rolled flat or cut into pieces.

Oats have been an important food crop for thousands of years, especially in cooler climates like Scotland and Ireland where other grains struggled to grow. Farmers also grow oats to feed horses, cattle, and other livestock. If you've ever given a horse a treat, it might have been an oatcake or a handful of oats, which horses love.

People often use oats in cookies, granola bars, and bread. Steel-cut oats, rolled oats, and instant oats all come from the same grain, just processed differently. The whole grain is nutritious and filling, which is why it's been a breakfast staple for so long.