Rarely has something so tiny generated such debate and caused so many international and cultural divisions.

Although embryonic stem cells are accepted to have enormous potential, especially in the treatment of diseases that are at present incurable, there are wide differences between countries and cultures in their regulations and attitudes.

At the heart of the issue is the fact that human embryonic stem cells are derived from a tiny bundle of cells, a blastocyst, that could generate a living human. Some consider the blastocyst to already be a human.

An analysis by the University of Minnesota suggests that countries with a permissive policy on human embryonic stem-cell research include Australia, Belgium, China, India, Israel, Japan, Singapore, South Korea and Sweden, as well as the UK. Those classed as having a flexible policy, including restricting research to fertility clinic embryos that are no longer needed for reproduction, include Brazil, Canada, France, Iran, South Africa, Spain, the Netherlands and Taiwan.

Countries with restrictive or no policies include Austria, Ireland, Norway, Poland, Germany, Italy and the United States. Restrictive policies range from prohibition of human-embryo research to permitting research on imported embryonic stem-cell lines only.

It is becoming clear that the scientific community has to win the support of people through education and dialogue.

When Professor Lee Eng Hin, a leading Singapore researcher, was asked what was the biggest threat to stem-cell research, he said: “It is important that everyone understands the challenges involved in stem-cell research but also realises that the potential benefits are tremendous.

“Scientific issues can be overcome but a positive public perception and support is essential. At the end of the day, scientists and doctors will have to find a safe way to use stem cells for treatment of diseases that have hitherto been incurable.”