Fossils are remains or imprints providing evidence of the previous existence of ancient fauna and flora. From a comparatively recent geologic era of just a few thousand years ago stretching in time to a period of many hundreds of thousands of years or more in the past is when fossil formations can be found. They have been discovered throughout the four corners of the world as infinitesimally small one-celled organisms to medium-sized mammals to massive dinosaurs demonstrating the vastly different dimensions fossils can embody.

A fossil holds a very similar form, except that its weight usually differs immensely from that of the original organism. Plant fossils can be found in rocks or as petrified wood. Besides fossils in rock, animal fossils can be teeth, hair, feathers, skeletons, claws and tusks and even preserved tissue. Insects can be encased in a resin, like amber. Sea life fossils can be teeth, bones, shells and coral, along of course, with rock fossils. In addition, the impressions left from the natural actions of the creature when it was living, such as, paw prints, tracks and trails can compose fossils. Even bodily functions, like eggs and stool, are considered part of the fossil record.

Most often the remains of prehistoric organisms are lost due to predators, scavengers or decomposition. Even so, under proper environmental circumstances, formation of fossils occurred. Sedimentary rocks consisting of types like sandstone, shale, coal and limestone are largely the sort of rocks which fossils can be found preserved inside.

There are several ways that fossils can form. One manner in which fossils develop is when water penetrates a shell or skeleton building up minerals inside which over time strengthens the structure. Another process permitting a fossil to form is when a creature is sealed inside a material that eventually hardens, like being froze in ice or encased in a resin. Similarly an animal can be trapped and covered by tar or volcanic ash. Another type of fossil is the complete drying of the creature inside and out causing a sort of mummy. Still another method of fossil formation is under heavy compaction. For instance, an animal dies and is promptly enshrouded and pressed down by sediment eventually solidifying to produce a rock fossil. One more fossil type is when the dead body of an animal has entirely vanished and all that remains is a hole in the rock just like the shape of the organism. Sometimes this hole loads up with different materials afterwards.

Besides being interesting and fun to look at, so much can be learned from the study of fossils. They teach us about the Earth's past and the ecosystems that prehistoric animals and plants lived in. Without fossils, we may never have known that certain species had ever existed at all. Sadly though, they make us aware that there are probably many fantastic creatures we will never know anything about since they were not preserved by fossils.