Charles Davis writes Story from BBC NEWS
The world's smallest book just one millimetre square is among a number of unusual volumes on display at Aberystwyth to mark World Book Day.
Old King Cole, a 12-page book of the famous nursery rhyme, is part of an exhibition at The National Library of Wales at Aberystwyth. The miniscule volume is one of only 85 copies printed by Scottish publishers in 1985 and can only be read using a microscope.
Among the other rare books on public view are the oldest book printed using moveable type in the 15th Century, the first printed book in Welsh, and also the smallest book in Welsh.
Sion Jobbins, marketing officer at the library, said the books would be on display for the next two weeks.