Amber is a hard, yellowish, and often see-through substance that forms from tree resin. Resin is a thick fluid that oozes from pine and fir trees when their bark is injured. The resin that formed amber came from trees that grew millions of years ago. Over time these trees and their resin became buried beneath Earth’s surface. The trees eventually decayed and disappeared. But the resin hardened further, until it became amber. Many pieces of amber contain the remains of insects or plants in the form of fossils. These living things were trapped in the resin before it hardened into amber. Scientists study these creatures to learn how living things have changed over millions of years.

Source: Britannica