Long run growth is characterised by complementary changes in the structure of the economy on both the supply and the demand side, such as the organisation, technology and sectoral composition of production, income distribution and consumption behaviour, and culture and institutions. In turn, these changes define the path of economic growth. We briefly overview the main empirical and theoretical aspects of the long run changes that have characterised the pattern of now industrialised economies. We show an example of how we can model these complex complementarities as an outcome of the interactions between economic agents using computational techniques, and discuss some theoretical results.