The paper offers a theoretical analysis of long-run economic growth as an outcome of structural changes. We model the microeconomic behaviour of firms in the final good and capital sectors, and the evolution of classes of workers/consumers. We carefully craft economic behaviour onto empirical evidence, and solve the model numerically. The results illustrate the microeconomic properties of the simulated growth patterns. In particular, we observe and explain the interactions between technological change, firm organization, income distribution, consumption behaviour and growth. We confirm the relevance and interdependence of these structural changes, and underline their microeconomic sources.