Stem cells are the cellular putty from which all tissues of the body are made. Ever since human embryonic stem cells were first grown in the lab, researchers have dreamed of using them to repair damaged tissue or create new organs, but such medical uses have also attracted controversy. Yesterday, the potential of stem cells to revolutionise medicine got a huge boost with news of an ultra-versatile kind of stem cell from adult mouse cells using a remarkably simple method. This timeline takes you through the ups and downs of the stem cell rollercoaster.

1981, Mouse beginnings Martin Evans of Cardiff University, UK, then at the University of Cambridge, is first to identify embryonic stem cells in mice.

1997, Dolly the sheep Ian Wilmut and his colleagues at the Roslin Institute, Edinburgh unveil Dolly the sheep, the first artificial animal clone. The process involves fusing a sheep egg with an udder cell and implanting the resulting hybrids into a surrogate mother sheep. Researchers speculate that similar hybrids made by fusing human embryonic stem cells with adult cells from a particular person could be used to create genetically matched tissue and organs.

1998, Stem cells go human James Thomson of the University of Wisconsin in Madison and John Gearhart of Johns Hopkins University in Baltimore, respectively, isolate human embryonic stem cells and grow them in the lab.

2001, Bush controversy US president George W. Bush limits federal funding of research on human embryonic stem cells because a human embryo is destroyed in the process. But Bush does allow continued research on human embryonic stem cells lines that were created before the restrictions were announced.

2005, Fraudulent clones Woo Suk Hwang of Seoul National University in South Korea reports that his team has used therapeutic cloning a technique inspired by the one used to create Dolly to create human embryonic stem cells genetically matched to specific people. Later that year, his claims turn out to be false.

2006, Cells reprogrammed Shinya Yamanaka of Kyoto University in Japan reveals a way of making embryonic-like cells from adult cells avoiding the need to destroy an embryo. His team reprograms ordinary adult cells by inserting four key genes forming "induced pluripotent stem cells".

2007, Nobel prize Evans shares the Nobel prize for medicine with Mario Capecchi and Oliver Smithies for work on genetics and embryonic stem cells.

2009, Obama-power President Barack Obama lifts 2001 restrictions on federal funding for human embryonic stem cell research.

2010, Spinal injury A person with spinal injury becomes the first to receive a medical treatment derived from human embryonic stem cells as part of a trial by Geron of Menlo Park, California, a pioneering company for human embryonic stem cell therapies.

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Stem cell timeline: The history of a medical sensation