The following article lists the cities and metropolitan areas with the greatest scientific output, according to the Nature Index. The Nature Index attempts to objectively measure the scientific output of institutions, cities and countries by the amount of scientific articles and papers published in leading journals. Differences in quality are taken into account. Only articles published in 82 selected quality journals are counted. All these journals are in the English language. They were selected by a committee. If authors from several institutions from different cities are involved in a scientific article, it is divided accordingly, assuming that all researchers were equally involved in the article.