Glass is an anthropogenic material that is amongst the most inimical to microbial growth. Yet, here on the glass roofs of Guildford Station a thriving microbial ecology has managed to establish itself (images above). I’m not sure what it is but it looks like the photosynthetic purple sulphur bacteria that you would usually find illuminated anoxic zones of lakes and other aquatic habitats or in Winogradsky columns. It’s as if the air fizzes with all manner of latent biological potential, in the form of its bacteria, that are just waiting to find an appropriate niche in which to thrive. Whatever this roof top ecology is made up from, it must be an exquisitely matched to the environmental niches because just a couple of yards away on the other side of the platform there is a very different one (images below). A fine example of my concept of microgeography.