Some dye visualisation of the Ahmed body at low Reynolds number (Re_L = 26000). This simple experiment shows the scale, location and shape of the separated region. Additionally, we can see some vortex shedding near the centre of the body. In fluid mechanics we often focus too much on the data acquisition side of experiments – taking copious amounts of data and then trying to reduce it to something that tells a story. With flow visualisation, however, we get a real feel for the flow and the physics that are at play before getting any quantitative data.