Since the emergence of life on Earth, organisms have exerted a significant influence on the Earth's environment, and conversely, the Earth's environment has also had a profound impact on organisms. We are conducting research to reconstruct paleoecosystems, the history of life, and the evolution of the Earth's environment, using biologically derived organic molecules preserved in sediments (molecular fossils: biomarkers) and organic-walled microfossils, including organisms that are difficult to preserve as fossils. In particular, to elucidate the evolutionary history of terrestrial life, we are also engaged in developing indicators using not only ancient sediments but also recent terrestrial and marine sediments, as well as biological samples.