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The geological record gleaned from scrutinizing ancient rocks is the only direct source of information regarding the physical, chemical, and biological evolution of Earth. Such studies provide information to geophysicists and geochemists who puzzle over planetary heat and structure, and to biologists who seek to place the element of time within their reconstructions of the emergence of phylogenetic diversity The past decade has seen a resurgence of interest in the first 2 billion years of Earth history. Reports emerge with increasing frequency regarding the nature and timing of the formation of the volatile envelopes of the planets, early bombardments and their contribution to the eventual chemical makeup of all planets, chemical evolution of the atmosphere, and the antiquity of the biosphere. Each of these is of intrinsic interest to science, and uncertainties over the details continue to uphold a reputation in the field of Archean studies for active, often strenuous debate.