The public has voted the X-ray machine as the best invention, ahead of the Apollo 10 space capsule and Stephenson's Rocket.
Out of nearly 50,000 votes cast, one in five people named it for having made the greatest impact on the past, present and future.
Ten of the most significant objects in science, engineering, technology and medicine were selected for the vote.
Information on all the items is found at the Science Museum in London.
The first three positions were filled by medical inventions or discoveries, the X-ray machine being followed by the discoveries of penicillin and the DNA double helix structure.
X-rays provided the first possibility of looking inside someone's body without cutting them open - a massive medical advance.
'Laying patients bare'
The particular X-ray machine in question - the Reynolds machine in the Museum's Making the Modern World Gallery - was a "do-it-youself" experiment by a father and son who were so inspired by news of the discovery of the X-ray that they set about building the equipment in their own home.
1st place - X-ray machines
2nd place - Penicillin
3rd place - DNA double helix
4th place - Apollo 10 capsule
5th place - V2 Rocket Engine
6th place - Stephenson's Rocket
7th place - Pilot ACE Computer
8th place - Steam Engine
9th place - Model T Ford
10th place - Electric Telegraph
Museum curator Katie Maggs said: "It's very inspirational to budding scientists to learn that an invention now declared the most important in world history could be pioneered by enthusiastic amateur inventors."
Professor Andy Adam, president of the Royal College of Radiologists, was delighted to learn of the result.
He said the X-ray machine had revolutionised medical practice and that the technology had now advance so much that we are reaching the era of the "transparent patient".
Culture Secretary Ben Bradshaw said: "Any competition that pits the Apollo 10 spacecraft against Stephenson's Rocket, and the DNA double helix against the Model T Ford, is bound to provide talking points aplenty.
"The public's choice of the X-ray machine as the winner is testament to our insatiable curiosity to find out how things work."
The poll was conducted as part of the Science Museum's events to mark its centenary. The 10 objects form a special Centenary Journey trail through the museum galleries.
Medical inventions were in the top three places in the poll
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