The first report of cultural behaviour in primates -potato-washing described in Japanese macaqueswas the starter point for 70 years of investigation of social learning in wild animals and has laid the foundations of animal culture studies. In this chapter, we review key findings now accumulated for many different monkey species and using a wide array of methodologies including observations in the wild, controlled experiments in captivity, and field experiments. Both observational and experimental approaches highlight the existence of technical, feeding, and social traditions in monkeys. Recent advances in modelling techniques enable a better understanding of when social learning is used and if the pathways of transmission follow specific biases such as payoff bias, conformity or learning from specific group members like higher-ranked or successful individuals. Technologies including environmental DNA metabarcoding, GPS loggers and artificial intelligence are promising new tools in evidencing group-level differences. Combining all these examples, we illustrate the diversity of cultural behaviour found in monkeys, confirming the saying 'monkey see, monkey do'!