For example, iron-gall ink, commonly used on ancient documents, is transparent to infra-red light and most visible in the ultraviolet region of the spectrum.

ECONOMIST: Monitor

It slipped enlarged photographs of the latent prints and the prints from Mr Mitchell into transparent plastic sleeves, and marked red dots on the sleeves to suggest which of Mr Mitchell's prints matched the latent ones and where.

ECONOMIST: Fingering fingerprints

Though the carbon nanotubes absorb infra-red light, they are almost totally transparent to the visible variety.

ECONOMIST: Monitor

By carefully tailoring the semiconductor layers, the researchers can make lasers that shine in two bands of infra-red light to which the atmosphere is highly transparent allowing the light to travel a long way.

ECONOMIST: Lasers

Each disc is covered in a transparent plastic coating (either blue, green, yellow or red) which lets daylight filter through.

WSJ: Daniel Buren's Bright Periphery | 'Excentrique(s) Travail In Situ' at the Grand Palais in Paris

But when the puffins get used to human presence, they return to their normal routine, landing close by, their beaks brimming with slivers of transparent- and silver-covered food that contrast brilliantly with the bright red of the beak.

BBC: Nature��s biggest treasure hunt