Hay is grass or other plants that have been cut, dried, and stored to feed farm animals during winter or times when fresh grass isn't available. Farmers harvest hay in late spring or summer when the grass is tall and nutritious, then let it dry in the sun before gathering it into compact bundles called bales.

For thousands of years, hay made it possible to keep horses, cattle, sheep, and other grazing animals alive through cold months when nothing grows. Before hay, many animals had to be slaughtered each fall because there wasn't enough food to sustain them. The invention of hay storage changed everything, allowing farmers to maintain healthy herds year-round.

You've probably seen those golden rectangular or round bales dotting fields in late summer. The phrase make hay while the sun shines comes from the urgent need to cut and dry hay during good weather: if rain soaks freshly cut hay, it can spoil or even heat up from bacterial activity when stored wet.

Hay shouldn't be confused with straw, which is the dried stalks left after harvesting grain. Straw works great for bedding but has little nutritional value, while hay is actual food for animals.