These days everything from your food and clothes to the medicines you take may well come from genetically modified plants or bacteria. The first generation of engineered organisms has been a huge hit with farmers and manufacturers – if not consumers. And this is just the start. So far organisms have only been changed in relatively crude and simple ways, often involving just one or two genes. To achieve their grander ambitions, such as creating algae capable of churning out fuel for cars, genetic engineers are now trying to make far more sweeping changes.