Earlier this month, two samples of mould that Sir Alexander Fleming used to produce penicillin sold for almost £25,000 at auction.
Contained on glass discs, the samples date back to the 1930s and are of huge historical significance; but as the purchasers chose to remain anonymous, we'll never know their reasons for buying.
But the mould is by no means the oddest thing ever to have gone under the hammer - here are seven of the weirdest ever auction lots.
World's most valuable pink diamond up for auction
The original Hollywood sign
The first 'Hollywood' sign went up in 1923; it originally read 'Hollywoodland', but the last four letters were later removed. It was replaced in the 1970s, but the original was saved and kept in storage - and was auctioned on eBay in 2005. It made a reported $450,400.
A dirty toilet
Not just any dirty toilet, this one was the property of reclusive Catcher In The Rye writer JD Salinger, and was put up for auction months after his death in 2010. It was listed for $1 million, although it appears not to have sold.
Why did Harry Potter book sell for £43,750?
Several ancient slices of cake, in fact. A slice of Queen Victoria's wedding cake made £1,500 at auction in 2015. Meanwhile, several pieces of Prince Charles and Princess Diana's wedding cake have gone under the hammer - not literally, obviously - making around £1,000.
Winston Churchill's dentures
Churchill's gold-plated dentures were sold at auction in Norfolk in 2010 for £15,200. They went to a Gloucestershire man who already owned the microphone Churchill used to announce the end of the Second World War.
Brad Pitt and Angelina Jolie's breath in a jar
In 2005, an unusual listing appeared on eBay - a jar claimed to contain Brad Pitt and Angelina Jolie's breath. Described in the listing as 'celebrity air', the price rose to over $75,000 - although there's no guarantee this wasn't just a prank.
Queen Victoria's size 26 bloomers sold at auction
Queen Victoria's bloomers
Three years ago, we reported on the sale of Queen Victoria's bloomers, which went for three times the estimate at £6,200. But the buyer certainly got plenty for his money, as the size 26 knickers had a 52-inch waist.
A person's whole life
Several people have tried this. The first was Australian resident Ian Usher, who attempted to auction off his house, possessions and job after splitting up with his wife. However, none of the highest bidders actually followed through. Since then, several other people have tried the same thing, but none seems to have had much luck.