Earth scientists can glean clues about the nature of Earth's ancient environments from a variety of clues: sedimentary textures and structures, chemical and isotopic compositions, microscopic to macroscopic fossils, and others. At Caltech we approach this problem from both ends of the time scale – working on modern analog organisms and environments to understand the signals they preserve, and on ancient sediments and rocks to try to decipher what the Earth was like thousands, millions, or billions of years ago.