This lecture is about what people now call “genetically modified” or GM foods. Or “biotech crops,” which means crop plants modified by modern molecular techniques. Another term that’s applied to them is “genetic engineering,” which is abbreviated GE. They’re also called GMOs (this stands for genetically modified organisms), and this is what I will call them here. In this lecture, we explore what all this means. We will define GMOs. We will set them in historical perspective, talking about how people have modified crops over some 50,000 years or so. We will show exactly what scientists do in the laboratory today and how they have modified crop plants to protect them from insects and diseases. We will inquire into their potential for causing harm to people, other organisms and the environment. We will discuss how and where they’re used. And we will ask why we need them and what they might allow us to do in the future.