Microbes dominated habitable environments on the early Earth for more than 3.5 billion years. The Great Oxidation Event (GOE) between 2.5 and 2.0 billion years ago (Ga) records the greatest period of enrichment of oxygen in the atmosphere and oceans. Also unprecedented at that time is the worldwide occurrence of columnar stromatolites in various rock types. While stromatolites likely hosted the cyanobacterial communities that produced O2, this has not yet been documented. Stromatolites are also morphologically diverse although the origin of different column shapes remains poorly understood. Organic residues in stromatolites that formed during this time period have the potential to preserve geochemical signatures of cyanobacteria. Is there a difference between the composition of organic matter in stromatolites formed before and after the GOE? It is the possible that the composition of organic matter in these stromatolites relates the observed stromatolite morphologies. Because of the microscopic size of the particles, a multi-technique approach is needed to determine the mineralogy and chemical compositions. Results and skills acquired will include petrographic analysis of Proterozoic carbonate rocks and micro-Raman analysis of organic particles and early diagenetic minerals. There will also be opportunities to use electron and ion microscopes to produce images of chemical compositions. Stable isotope compositions of C and N will also be measured to determine metabolisms.