In order to understand how well the features of leaves reflect the climate they grow in, we need to study leaves from trees growing in many different climates. Ginkgos are the perfect plant for this. While their natural range is restricted to China, ginkgo trees can now be found all over the world as humans have and continue to transport them. Ginkgos also have a rich fossil record dating back to the Jurassic Period, meaning we can apply what we learn about reconstructing climates from today's ginkgos to the past hundred million years through beautifully preserved fossil leaves. We're looking for citizen scientists to send us leaves from their communities! Fossil Atmospheres is a National Science Foundation-funded project focused on determining how the cells of leaves on ginkgo trees have changed over time and how we can use this knowledge to learn about the ancient atmosphere of the Earth. This project, based out of the National Museum of Natural History and the Smithsonian Environmental Research Center, brings together researchers at the Smithsonian Institution and citizen scientists in climate change research.