Science has achieved tremendous success over the centuries, partly because the complexities of the Earth, the physical processes that sustain the planet, and the enormity of life were separated into disparate fields of study—mathematics, physics, chemistry, biology, and geology, to name only a few. Scientific compartmentalization was initially necessary to impart enough focus to make progress on complicated issues. However, as the knowledge base grew, it became more and more difficult to separate life and the history of the Earth, and vice versa. We now understand that to investigate the Earth's surface as an abiologic system is folly: Life and Earth processes are intimately linked. Hence, a new field was born at the interface between biology and geology: geobiology. As a field, geobiology seeks to understand the intersection of life and the rock record across Earth's history: how organisms influence the physical Earth and vice versa, and how the marriage of physical and biological processes have transformed our planet over its long history. The assessment of life's macromolecules of DNA, RNA, polysaccharides, proteins, and lipids, and their potential recalcitrance in an ecosystem, has opened up the field of geobiology to lead us toward a solid explanation of where life came from, how life has altered the planet, what may be possible for life elsewhere, and what represents one of the reasons for the explosion of geobiologic studies today. Here we outline how molecular biology has transformed our understanding of geobiology, describing a few of the essentials needed to understand geobiology and exploring an example of a modern geobiologically relevant system: a living stromatolite from the shore of a geothermal hot spring in Yellowstone National Park, Wyoming, USA.