Europe's highest court last month clarified the law on the patentability of processes involving research on human embryos and stem cells. The case was referred to EU the Court of Justice by the German Federal Patent Court, which had been asked to resolve a dispute between patent owner Oliver Brüstle and environmental campaigning group Greenpeace. Brüstle filed a patent application in 1997 relating to his research work on isolated and purified neural precursor cells produced from human embryonic stem cells used to treat neurological diseases. Greenpeace claimed the patent was invalid because it covers processes for obtaining precursor cells from human embryonic stem cells. The Court of Justice ruled that a process that involves removal of a stem cell from a human embryo at the blastocyst stage cannot be patented. The judges said that the use of human embryos for therapeutic or diagnostic purposes which are applied to the human embryo and are useful to it is patentable, but that their use for purposes of scientific research is not patentable. In reaching its conclusion, the Court defined embryos widely, saying that they begin right at the earliest stage of development of a human being. The German court must now decide whether the stem cells used in Brüstle's patent are classed as a human embryo.