This chapter explores the notions of capital, innovation, and investment in urban occupations during the Roman period, viewed through archaeological data. With regard to these three factors, it focuses not upon macroscopic changes in the entire technological system but on ‘microscopic’ variations in urban occupations, based on a thorough analysis of the chaînes opératoires involved in the various urban crafts and trades. Leaving aside the difficulty of any attempt to draw a realistic synthesis, it shows that the quantitative and qualitative diversity of shops and workshops should be understood as a performant indicator of the urban economy: when added together, the different forms of real capitalization would appear to be a generative force.