Abstract: A scientist is on a long plane flight, and the stranger sitting next to her asks her what she does. She says she's an immunologist. “Oh really”, says her seat mate, “what do you work on?” “The mechanism of antigen presentation by class I MHC molecules”, she replies with a sinking feeling. “How interesting”, he murmurs, pulling a copy of War and Peace from his bag, and another opportunity for spreading the scientific gospel evaporates. This is not a true story, but it easily could be. Half the graduate students I talk to say that even their parents don't understand anything about the research they're doing. The language gap between ‘us’ and ‘them’ fuels two myths: the public's opinion that modern biology is incomprehensible, and the biologist's belief that the general public just doesn't care about science. I strongly believe that both points of view are false. People do care about how they, and plants, and animals work, and what most of us do is pretty easy to explain. The biggest barrier between us and the public isn't scientific jargon, but an unwillingness on both sides to make a serious effort to talk and listen to each other. To communicate with the public, we have to practise two essential skills of the successful tourist: translation, and paring a message down to its essentials. The simplest translation is to connect our research to human biology and illness. Lots of experiments are ultimately relevant to two pressing questions: how did the fusion of a sperm and an egg lead to me, and how can I tell if I'll get the disease I'm worrying about now? Were you the hypothetical traveler, you could say, “I'm trying to understand why having measles once protects one from ever having it again”. Your seat mate may still prefer War and Peace, but there's a reasonable chance he might ask: “Then how come I get flu every year or two, but never get measles again?”, and initiate a dialog. For the Tolstoy fan, the only limits are his patience and the length of the flight. For you, the challenge is to simplify, by avoiding most of the sacred details that your work revolves around, and by using analogies that will explain key principles in everyday language. For the greater good of science, you can revel in sweeping generalizations that would be unpardonable in a scientific paper. If you think the stretch from your work to your seat mate's health is too far, think of a cute analogy for what you do. If you work on how cells make sure they finish DNA replication before entering mitosis, you can say you are trying to understand how cells make sure they've got their socks on before putting on their shoes. Explaining yourself to non-scientists is like riding a bicycle: almost impossible at first, but easier with practice. Next time you're stuck in a boring seminar, concoct a simple explanation of your work to try out on your parents. Why should we take the time and trouble to explain what we do? For a lot of us, Josephine and Joe Q. Public support our research and buy our groceries. Our patrons are entitled to know what we are doing with their money (at least while we're at work). Also, explaining science is fun. A surprising number of non-scientists share our childish delight in figuring out how things work, and their questions often force us to confront unspoken (and perhaps incorrect) assumptions. Finally, explaining ourselves should get the public on our side. We all believe that if adults understood how today's basic research can be tomorrow's medicine or greener world we'd have better funding for science, and that if kids saw the beauty and excitement of scientific discovery we'd have more scientists and fewer lawyers. Explaining what science is and why we do it is the only way to reduce the credibility gap between scientists and non-scientists. As the second millennium approaches, science and technology are no longer seen as entirely good things. Significant fractions of the public believe we are up to no good, and that we don't want them to know what particular sort of “no good” it is. Basic scientists argue that it's not science but its applications that kill people or destroy landscapes. If you don't understand science you can't understand this argument. All you can do is accept it because you believe people in white coats, or reject it because (like many scientists) you don't buy abstract explanations from entrenched authorities. If we cannot escape from our own jargon, it's hard to avoid the charge that we invented it to hide our work from the public behind a lot of Greek and Latin roots. However it got there, the credibility gap supports two dangerous beliefs: the pessimist's dark suspicion that we're out to destroy the world, and the optimist's rosy conviction that science will allow the indefinite survival of a civilization that believes that tomorrow never comes. The only way out is to explain to the public what we're doing now, tell them how much we still don't understand, and give our best guess about where today's knowledge will lead. By fulfilling these obligations, we can show Joe and Josephine the beauty that captivates us. More importantly, we can help them make informed decisions about the social and political questions that science and its applications create. Andrew Murray, Department of Physiology, University of California, San Francisco, USA.