The chip - around a square centimetre in size - would run on very little power.

BBC: Scientists develop 'nose-on-a-chip'

I-mod pixels measure a mere 30 microns by 40 microns (a micron is a millionth of a metre), more than 80, 000 of them could fit in a square centimetre.

ECONOMIST: Displays: The fluttering of tiny pixels | The

With cooling, the cells can manage an output of 70 watts a square centimetre a record, according to IBM, and a demonstration that plumbing, too, can be a high-tech form of engineering.

ECONOMIST: Monitor

European Union guidelines say that earrings are supposed to contain less than 0.05% nickel by weight and should not release more than 0.5 micrograms of the metal per square centimetre of their surface area per week.

BBC: Earring

Pieces of slime mould, an amoeba-like organism, were enticed through a 30-square-centimetre (five-square-inch) maze by the prospect of food at the end of the puzzle.

BBC: When slime is not so thick