Scientists are toasting the anniversary of a great medical breakthrough by raising a mouldy cup of coffee.
Wednesday marks 75 years since Sir Alexander Fleming discovered penicillin thanks to a discarded dirty dish in his laboratory.
To commemorate the milestone, the Royal Society of Chemistry (RSC) wants people to send in photographs of furry coffee cups, of the kind commonly found lurking in the corners of offices and factories.
The most spectacularly rancid example will win the owner a night of culture in, hopefully, cleaner surroundings.
Sir Alexander Fleming discovered penicillin at St Mary's Hospital, London, on 3 September 1928 after leaving a dish in his laboratory one summer.
The culture which grew on its surface opened the way to the development of a medicine which relieved suffering during World War II and went on to help hundreds of millions of people.
This filter was left for three months and stank of alcohol
RSC spokesman James McNish said: "The culture that developed on Fleming's laboratory dish has much in common with those ageing, ownerless coffee cups languishing on shelves and workstations in British offices and in factories.
"This competition is a way of illustrating the point that science sometimes involves some luck and happenstance.
"We do not recommend that people leave filthy coffee cups near their computers for weeks or even near lab equipment.
"Safety and cleanliness is generally the far better route to good results, but the penicillin story is a rare example of progress through messiness."
Send us your mould
BBC News Online would like to feature the best examples of our readers' disgusting coffee cups.
If you have a particularly impressive culture lurking in your home or workplace, please send us a photo to: firstname.lastname@example.org.
We will forward all entries to the RSC and compile a gallery of the best growths.
A particularly impressive entry from an office in Russia
The culture on top of the leftover coffee must be clearly visible and, although BBC News Online would like examples sent in immediately, the RSC will accept pictures until 10 September.
The early closing date has been set to prevent people cheating and growing their own cultures.
The winner will be announced during National Chemistry Week in November.