Searching for life outside our own planet compels us to distinguish between the types of planetary environments that can host life, and those that cannot. This search not only requires a robust understanding of the limits of modern life, but also plausible models of the evolution of abiotic chemistry that eventually gives rise to life. Current research seeks to understand the origin and composition of organic compounds in space, the emergence of life on Earth, the extent of life in Earth’s extreme ecosystems, and the potential for life elsewhere in the solar systems.