The Archean-Proterozoic (AP) transition is marked by remarkable changes in Earth system processes including plate tectonics, glaciations and geochemical conditions of Earth’s ocean-atmosphere system. Evidently, life navigated its way through these major fluctuations into the Proterozoic, towards greater complexity and diversity. This presentation will discuss major changes in Earth system processes and the biosphere, including the reciprocal nature of their interactions, during the AP transition. Several geochemical proxies have provided useful insights into this transitional period. While not all geochemical proxies are in agreement with one another, they do provide a unique perspective on different aspects of Earth system processes such as redox conditions, nutrient supply, biological evolution and economic mineralisation. This presentation will focus on the chemistry of pyrite in marine black shales (~2500 pyrite analyses) alongside other existing geochemical proxies with an aim to highlight major controversies surrounding this transition period. For instance, whether the Great Oxidation Event was a sharp event at 2.33 Ga or a more prolonged event, beginning much earlier (~2.7 Ga). Geochemical trends (bio-essential trace metal archives) will also be discussed in light of biological evolution during the AP transition. While organisms of definite eukaryotic origins have been recorded in the Mesoproterozoic rock record, can we reconcile geochemical conditions of the AP transition with the evolution of proto-eukaryotes or eukaryotic cellular machinery?