Trouble with Lichen: Where air quality permits, lichens are a ubiquitous microbiological component of our urban environments. They are composite microorganisms comprising symbiotic partners, a fungus (the mycobiont) and a photosynthetic organism (the photobiont; usually an algae or cyanobacterium). Lichens produce an extraordinarily complex mixture of chemicals and whilst the function of many of these is not known, some have been used for the production of litmus, medicines and textile dyes. The plot of John Wyndham’s “Trouble with Lichen” concerns a young woman biochemist who discovers that a chemical extracted from a strain of lichen can be used to slow down the ageing process, enabling people to live to around 200–300 years and in his novel Wyndham speculates how society would deal with this prospect. This is a diptych of an ecology of lichens, an image taken using daylight (how we perceive them) and one taken using an ultraviolet light source to emphasize their important but usually invisible chemistry.