The emergence of districts in nanotechnology represents a new pattern of scientific development. The factors affecting their growth are analysed to understand the drivers of economic development. By analyzing the top 200 nano-districts, Nanotrendchart sheds light on the clusterization process: academic production is seen to be highly concentrated, with fifteen districts representing over half of published articles; Asian districts are clearly growing significantly faster than those elsewhere; and district growth in the domain of engineering and physics is more rapid than in other disciplines. Scientific diversity, actors diversity as well as the degree of openness of the cluster influence their evolution. Highly specialised clusters witness lower growth rates. For more informations : http://www.nanoeconomics.eu/