The digital era creates new possibilities for observing humans’ behaviour, especially the one expressed on the Internet, but we also leave traces during everyday activity by making phone calls, using GPS devices or using any kind of transportation. People who meet together or communicate over the Internet or other channels constantly exchange information, rumours, spread opinions and attitudes. Sometimes it is just an information that is being passed from one to another, but it may also become the beginning of a huge change, either of an individual or even of the whole society – but in both cases it starts with becoming influenced or influencing others. Social influence is the process of a complex nature which involves our location in social network, the network structure and dynamics, time and psychological and sociological factors. At the level of an individual it is rather a psychological process but at the network scale it is strongly dependent on the network structure and its dynamics. Hence, studying social influence is a challenging interdisciplinary task, which, if succeeded, leads to better understanding of the surrounding world.