If you have a fossil, you can tell how old it is by the carbon 14 dating method.
This is a formula which helps you to date a fossil by its carbon.
Sometimes cells of the plant are even visible if the cells were filled with water.
Carbon film fossils normally depict fish, crustaceans and plants.
After 5600 years, if we start with a gram, we end up with half a gram.
The tool's creators hope it will help officials prosecute those who harvest and sell ivory illegally.
"Our dating method is affordable for government and law enforcement agencies and can help tackle the poaching and illegal trade crises," geologist Kevin Uno told Columbia University.
There's always some carbon-14 in the atmosphere, but during the Cold War, aboveground nuclear tests doubled the amount of carbon-14 in the environment.
Plants incorporate carbon into their roots, stems and leaves as they grow.