In order to better understand the effects of anthropogenic climate change, we paleoenvironmental researchers look back into the Earth's history and investigate how and why the Earth's climate has changed. Paleosols and lake sediments, among other things, help us to do this because these climate archives store information about past climate and environmental changes, even after tens of thousands of years. Our research group has specialized in so-called biomarkers ("molecular fossils") and their hydrogen and oxygen isotopes. We explain clearly ("hands on" ) how these laboratory methods work and how we are able to reconstruct climate changes and the influence of humans on different temporal and spatial scales.