Firms with different scope of technologies experience different firm growth. Understanding such heterogeneity requires knowing not only what drives technologies' scope but also why these drivers remain different across firms. I propose inventor specialization as a driver of technologies' scope: firms with more specialized inventors create narrower scope technologies. I also propose that these narrower scope technologies themselves in turn induce these firms' inventors to remain more specialized. I empirically demonstrate this two-way interrelationship in the U.S. communication equipment industry using policy shocks as natural experiments and a new measure of scope. This interrelationship has important implications for why resources and organization appear isomorphic within a firm but heterogeneous across firms. t © 2013 John Wiley & Sons, Ltd.