The fossilized remains of once-living organisms -- animals, plants and humans -- offer scientists a glimpse into the past. Fossils have long fascinated both paleontologists and enthusiasts for their ability to tell a story of a time long past. Most fossils show the shape of activity of extinct creatures and human ancestors, but some come from species that exist today. In paleontology, fossils do not just describe the bones or skeleton of an organism, they are used to classify the preserved remains of any impact organisms had in their environment – which also includes footprints, feces, and other elements.

The word ‌fossil‌ comes from the latin word ‌fossilis‌ meaning “something that is dug up.” The study of fossils is paleontology, and those who study fossils are called paleontologists. There are many types of fossils found all across the globe from Ethiopia to Argentina often found by fossil hunters and professional paleontologists. Fossils are commonly stored in natural history museums where scientists and geologists use them to describe the history of our world. Here are ten fun facts about these amazing scientific tools and discoveries; these fossil facts will cover everything from unknown types of fossils to some of the modern impacts of paleontology and fossilized matter.

Most of the organisms that died out long ago never became fossils because conditions need to be just right. Many fossils form on the seafloor, an animal dies, and sinks or gets swept to the bottom of the ocean, where its body rots away. Over time, the sediment around the bone hardens and the bone dissolves, forming a kind of mold. The water slowly deposits its minerals in the mold, making a fossil.

While some fossils show the skeleton of a long-dead creature, others are more subtle. Sometimes when a dinosaur stepped in muddy areas, sand filled the tracks before they washed away. With time the sand hardens, leaving behind a fossil of a footprint, called a trace fossil. From these, scientists learn about the behaviors of extinct species. The fossilized feces of an organism (called coprolites) are also types of trace fossils.

Body fossils are likely more familiar. They are an imprint of the actual structure of once living things. Dinosaur bones, mammoths, and sea creatures have all been preserved as body fossils through a variety of natural processes, enabling us to study them millions of years later.

There are also a huge variety in the organisms that are fossilized. Ammonites are were smaller shelled organisms, while dinosaur fossils (like Tyrannosaurus rex or Sauropod remains) can reach many tens or even hundreds of feet in length.

Whether the fossils are of humans or dinosaurs, they can teach scientists much about species and cultures that existed in the past. Scientists use fossils to make educated guesses about the evolution of different species, and what the climate was like in eras long past.

Scientists also use fossil information to form what is called the fossil record. These fossils describe the geologic time periods of the earth. The geologic history of the earth is described in many levels, with eras, periods, and epochs structuring some of the most recognizable times in geologic history. Dinosaurs lived during the Mesozoic era, which was then divided into the Triassic, Jurassic, and Cretaceous periods. In natural history, paleontologists often separate these divisions of time by mass extinction events or times of great geological change.

Researchers have a few ways of telling the age of a fossil, depending on the rough estimate of when it formed. For instance, aging particularly old fossils requires Carbon-14 dating, a process by which scientists study the radioactive decay of elements in the fossil. Scientists can age more recent fossils by a process called the molecular genetic clock, which compares the differences in DNA between a fossil and similar species alive today. Because DNA rapidly decays, it can only be used on newer specimens.

As these fossilized species no-longer exist, scientists can really only guess about the true nature of the creatures from which they came. While in previous years, scientists believed dinosaurs to be scaled, recent interpretations of fossils suggest they had feathers.

Scientists studying sedimentary rocks on Greenland found small graphite micro-particles believed to be the fossilized remains of byproducts produced by ancient bacteria, one of the earliest forms of life from 3.7 billion years ago.

In 2017, scientists discovered the remains of what they now believe to be the world's largest land animal. Called ‌Patagotitan mayorum‌, the fossilized remains suggest that the long-necked creature was 120-feet long, and possibly weighed 69 tonnes, over 150,000 pounds. Even creepy-crawlies were larger in pre-history. University of Manitoba paleontologists found the remains of a 28-inch long trilobite while searching for fossils near Hudson Bay.

After a while, some fossilized species stopped showing up, suggesting that those species went extinct. Scientists date one such event to 65 million years ago and suggest that a giant meteorite crashed into Earth and killed many of the species. Fossil records also exist for the species that survived this event, and how it changed their physiology.

Massive lumbering dinosaurs did not create fossil fuels. Rather, it was microscopic organisms called diatoms. Fossil fuels, a non-renewable resource, formed from these tiny creatures dying in large numbers. Pressure and temperature on the sedimentary rock which covered their remains converted the remaining carbon from their bodies into fuel.

Like fossil fuels, fossils themselves are becoming increasingly rare. Since it takes a long time for them to form, and they form under specific conditions, the reservoir of fossils in the Earth grows smaller and smaller each time a scientist takes one out of the ground.