A search for the filthiest coffee cup is the latest publicity stunt from the Royal Society of Chemistry. The society has launched the search to mark the discovery of penicillin 75 years ago. To qualify, the mould floating on top of the coffee must be clearly discernible. Office staff are invited to mail images - but not physical specimens - to Culture Shock, Royal Society of Chemistry, Burlington House, London S1J OBA by September 10. Images can be emailed to: emsleyb@rsc.org