The Heliospheric Imagers on board NASA’s twin STEREO spacecraft show that coronal mass ejections (CMEs) can be incredibly complex structures. To explore this complexity, we created a citizen science project, in collaboration with the Science Museum, where participants were shown pairs of CME images and asked to decide which appeared to be the most complicated, or complex. We then ranked all the CMEs in order of complexity. This complexity ranking revealed a surprising result; that the annual average complexity values follow the sunspot cycle. Here we present our findings and investigate the factors which cause a CME to be classified as ‘more complex’.