When we search for life beyond Earth, we have to figure out what we could measure that would tell us that life was, or is, there. And the starting place for that search must be Earth itself, the only place where we know for sure that life has lived. Every rock tells a story, and so does each fatty acid called a lipid. Your cholesterol, which is part lipid and part protein, could last for billions of years, and contains the information that you are a mammal. Could we find lipids beyond Earth? NASA astrobiologist Lindsay Hays explores this and other topics in her research. She also discusses places interesting for the search for life in our solar system and beyond.