Understanding the diversity of microbial activities in the environment is a fundamental target of geobiological research. Lipid biomarkers can serve as robust molecular tracers to study the composition of microorganisms and their metabolisms. To make lipid biomarkers the powerful tool of geobiological study, my research will focus on 1) developing efficient analytical protocols to detect, identify and quantify lipid biomarkers in various samples; 2) understanding the biological sources, transportation and preservation of lipids in sediment records; 3) demonstrating the biosynthetic pathways and biological function of lipids.