The Archean Eon is the second eon. Journey into Earth's past with a vibrant Archean Eon poster, exploring the time when simple, single-celled organisms—bacteria and archaea—first appeared. Cyanobacteria produced oxygen through photosynthesis. The Archean atmosphere lacked free oxygen, but over time, oxygen levels began to increase. Explore Archean Rocks- Greenstone Belts, microbial mats, and stromatolites. File Formats:PDF formatEPS vector format for flexibility. Vector files are scalable to any