From birth to death, human beings are hard-wired to connect to other human beings. Face to face contact matters: tight bonds of friendship and love heal us, help children learn, extend our lives and make us happy. Looser in-person bonds matter, too, combining with our close relationships to form a personal 'village' around us, one that exerts unique effects. And not just any social networks will do: we need the real, face-to-face, in-the-flesh encounters that tie human families, groups of friends and communities together.