Slowly does it

This lump of concrete is from a gun emplacement that was blown to smithereens at the end of the second world war. They certainly knew how to mix good concrete in those days - sixty odd years later the lump is still in very good condition. The lichens have started to make some progress in colonising the surface, but not much. However, lichens play a long game and are in no hurry! As Bill Bryson so cleverly puts it, in his A Short History of Nearly Everything, "Lichens are just about the hardiest visible organisms on Earth, but the least ambitious."

The detail will be best appreciated through the use of the considering-glass.