Working together with designers Rachel Wingfield and Mathias Gmachl, we explored new ways of representing the molecular world at this year's Science Festival in Cambridge. We invited people to colour a 2.20 x 6 metre mural of a mitochondrial network. Children of all ages and adults engaged in this mitochondrial paint-by-numbers event. The first step was, via a computer test, to find out which colour each visitor preferred. The mural was divided into 300 hexagons. The areas in each hexagonal were coloured according to shades and numbers, leaving the final image of the mitochondrial network represented by a multi-coloured structure.