Once a fossil is back in the lab, the work has only just begun. Paleontologists and lab technicians clean the fossils, so they can be studied. They inventory and catalog all the fossils. Each one gets a number and is added to the collection database. This allows the fossils to easily be tracked and identified. The fossils are prepared for storage or for an exhibit. Sometimes paleontologists will make a mold or a cast of the fossil that can be used in a display or a program. After all this work is done paleontologists, other researchers, artists, and students can observe and study the fossil. This research is used in different ways including to teach college and university classrooms, to write journal articles and books, to develop museum exhibits, and to create public programs. These fossils are used as evidence in the research paleontologists do to develop theories of the environment in which plants and animals lived, to compare changes in plants and animals over time, and variation in different life forms.