The ability to clone embryos was perfected by scientists in Scotland in the late 1990s and the ability to grow stem cells into tissues and organs is being developed12 by American researchers.

• 克隆胚胎的技能在20世纪90年代后期由苏格兰科学家研究成功并日臻完善，把干细胞培养成组织和器官的技术正由美国研究人员加以开发。