Stromatolites or stromatoliths are layered mounds, columns, and sheet-like sedimentary rocks that were originally formed by the growth of layer upon layer of cyanobacteria, a single-celled photosynthesizing microbe. Fossilized stromatolites provide records of ancient life on Earth.
Could you clarify the question a little more, do you want the order from oldest to youngest. Or do you want just the oldest part and the youngest part of the brain?.