British scientist Robert Edwards, the man who devised the fertility treatment IVF, has been awarded this year's Nobel prize for medicine.
His efforts in the 1950s, 60s and 70s led to the birth of the world's first "test tube baby" in July 1978.
Since then nearly four million babies have been born following IVF.
The prize committee said his achievements had made it possible to treat infertility, a medical condition affecting 10% of all couples worldwide.
Prof Edwards, 85, began his fundamental research over 50 years ago.
He soon realised that fertilisation outside the body could represent a possible treatment of infertility.
Other scientists had shown that egg cells from rabbits could be fertilised in test tubes when sperm was added, giving rise to offspring.
Prof Edwards went on to refine this technique for humans together with Patrick Steptoe, who died in 1988.
Their success means that today, the probability of an infertile couple taking home a baby after a cycle of IVF today is one in five, about the same that healthy couples have of conceiving naturally.
The pair faced numerous challenges in their quest, including opposition from churches and governments, as well as scepticism from scientific colleagues.
They also had trouble raising money for their work, and had to rely on privately donated funds.
But they went on to develop "a milestone of modern medicine", said the Nobel Assembly at Sweden's Karolinska Institute, which awarded the prize.
Bringing hope to millions
"Today, Robert Edwards' vision is a reality and brings joy to infertile people all over the world," the assembly said.
Prof Edwards, who is ill, was not available to speak to the media.
"Unfortunately, Prof Edwards is not in good health at this time," Nobel committee member Goran Hansson told a news conference.
"I spoke to his wife, and she was delighted. She was sure he would also be delighted."
The first IVF baby, Louise Brown, who is now 32, said: "Its fantastic news. Me and mum are so glad that one of the pioneers of IVF has been given the recognition he deserves.
"We hold Bob in great affection and are delighted to send our personal congratulations to him and his family at this time."
Professor Basil Tarlatzis, past-president of the International Federation of Fertility Societies, said: "This is a well deserved honour.
"IVF has opened new avenues of hope for millions of couples throughout the world.
"Edwards and Steptoe were real pioneers, and the award of the Nobel Prize honours not just their work, but the whole field of reproductive science.
"After their breakthrough work, Robert went on to nurture the development of the assisted reproduction.
"No-one deserves this award more, and we congratulate him."