The experience of meeting a complete stranger with whom we have apparently little in common and ï¬nding unexpectedly that we share a mutual acquaintance is one with which most of us are familiar—“It’s a small world!†we often say. In the 1960s, noted psychologist Stanley Milgram quantified this small world phenomenon by demonstrating that randomly selected individuals from almost anywhere in the United States were “connected†via a chain of no more than six intermediate acquaintances. In this talk, we will analyse the social network models proposed by “Watts & Strogatz†and “Klienberg†that attempt to explain this phenomenon.