. >> reporter: that's journalist eric weiner. for his new book, "the geography of genius," he traveled the world and back in time, a museum seemed a fitting backdrop to hear what he found. first stop, ancient athens.>> at global cities in the world and so they would open their doors to foreigners, resident aliens, who even though they knew they posed some sort of national security risk, they invited them in. >> reporter: and became cosmopolitan, the first necessary ingredient for the genius cluster every place would like to have, says weiner. unsurprisingly, the head of harvard's center for international development agrees. >> i study how places become good at different things, and i focus on how places change the things they're good at, evolve. >> reporter: professor ricardo hausmann. >> and what i find is that they tend to diversify into things that are somewhat related but somewhat more complex or more advanced. and in process of diversifying they rely enormously on talent that came from the outside. >> reporter: although note