The power of agent-based models is that they allow the researcher to ‘grow’ a system from the bottom up. This allows expressing all kinds of individual differences and preferences. The drawback is that an agent-based model is itself complex. Gert Jan will present a typology of twelve iconic patterns produced by agent-based models (e.g. Tragedy of the Commons, Fixes that Fail). It can guide modellers in thinking about patterns that occur in the systems they study, or about mechanisms that may cause these patterns.