The Royal Mail has launched the world's first "intelligent" stamp, the first to work with image recognition technology.
The stamp, part of the Royal Mail's latest Great British Railways edition, will launch online content via an iPhone or Android smartphone.
Users place the camera over the stamp, which then launches the online content.
The Royal Mail said intelligent stamps "mark the next step in the evolution of our stamps, bringing them firmly into the 21st Century."
People can use the stamps via the Junaio application, which contains a Royal Mail channel which activates the phone's camera.
Royal Mail has created a short film of Bernard Cribbins reading WH Auden's poem Night Mail for the launch, first made famous in the 1936 documentary film of the same name about the London to Glasgow postal train.
Mr Cribbins said: "WH Auden wrote the Night Mail poem in 1936 for the Post Office's own blockbuster film of the same name, which has for years remained in the hearts and minds of many.
The application is available in the iTunes store and Android Market free of charge.
The Royal Mail's Philip Parker said: "This is the first time a national postal service has used this kind of technology on their stamps and we're very excited to be bringing intelligent stamps to the nation's post.
"Royal Mail's special stamps mark key events and anniversaries in the UK's heritage through a programme which aims to be both educational and informative.
"Through Intelligent Stamp technology, our stamps will open up to a whole new world of information, interest and fun to collectors and the millions of people who will receive them on letters in the coming months alike."
The technology will also be made available on selected future special stamps.
Source: BBC - Yorkshire Evening Post
Also: Night Mail