Without doubt, there is a widespread usage of visualisations in science. However, what exactly the epistemic status of these visual representations in science may be remains an open question. In the following, I will argue that at least some scientific visualisations are indispensible for our cognitive processes. My thesis will be that, with regard to the activity of learning, visual representations are of relevance in the sense of contributing to the aim of scientific understanding. Taking into account that understanding can be regarded as an epistemic desideratum in its own right, I will argue that, at least in some instances, no understanding can be achieved without the aid of visualisations. Consequently, they are of crucial importance in this process. Moreover, to support this thesis we will make use of some findings in educational psychology.