It's an exciting feeling to see a fossil in a museum. Well, to answer this, there are four major ways in which a fossil can be preserved. Petrification occurs when a living object is slowly turned to stone of a huge number of years.
Minerals seep through the organic matter is an object, filling it completely.
Then the organic matter rots away, but a mineral version of the fossil is left. This process usually works best in the fossilization of trees. Some of the most famous petrified trees are in California, and contain huge rings that describe ancient eras. Molds Molds are literally molds of an animal. Sometimes animals became trapped in mud, dirt or clay.