Scientists at Cambridge University have found a way to mimic the colours on tropical butterfly wings, which may make bank notes harder to forge.
The team made structurally identical copies of the scales on wings, which created the same iridescent colour when light bounces off them.
Mathias Kolle described the discovery as unlocking one of nature's secrets.
"These structures could be used to encrypt information on banknotes to protect them against forgery," he said.
"We still need to refine our system but in future we could see structures based on butterflies' wings shining from a £10 note or even our passports."
Mr Kolle, working with Professors Ullrich Steiner and Jeremy Baumberg, studied the Swallowtail butterfly whose wing scales are composed of intricate, microscopic structures that resemble the inside of an egg carton.
Because of their shape and the fact that they are made up of alternate layers of cuticle and air, the structures produce intense colours, the university said.
The butterfly may also be using its colours to encrypt itself, appearing one colour to potential mates but another colour to predators.
Mr Kolle explains: "Seen with the right optical equipment these patches appear bright blue, but with the naked eye they appear green.
"If its eyes see fellow butterflies as bright blue, while predators only see green patches in a green tropical environment, then it can hide from predators at the same time as remaining visible to members of its own species."