An international conference opening on Sunday in South Africa aims to develop a revolutionary technology to curb the spread of HIV and Aids.
Aids campaigners marched to mark the start of the conference
More than 1,000 scientists will gather in Cape Town over the next four days to study a product known as microbicides.
The product, which can take the form of a gel or cream, releases an active ingredient designed to kill HIV during sexual intercourse.
Scientists hope to have microbicides on the market within the next four years.
Development of the technology began 15 years ago, and the conference will hear about the progress being made in what scientists say is possibly the most productive area of research in the fight against HIV and Aids.
They believe microbicides could have a major impact in the fight against Aids, especially in Africa, where women bear the brunt of the disease.
They are being developed because its often so difficult to insist that condoms are used during sex.
"It's not always possible for people to negotiate condom use in many different circumstances," said Professor Helen Rees, head of the reproductive health unit at the University of Witwatersrand in Johannesburg.
"So there was obviously a need to have methods that were potentially hidden, could be female-controlled, but also methods that would make a condom itself even safer."
Microbicides have been shown to be effective in the laboratory, and to have no significant side effects.
Large-scale trials are now under way to see if they work with real people in countries across Africa, as well as India.
But so far, the work is being funded by the American and British governments, in partnership with the Bill and Melinda Gates Foundation.
Pharmaceutical companies have shown little interest, since most Aids patients are in the developing world and have little money to spend on these products.