An attractive strategy for single-molecule DNA sequencing is to pass single-stranded DNA through a nanopore in a graphene monolayer. Here, the rings of carbon atoms in the graphene are depicted as hexagons, and the diameter of the nanopore is about 1.5 nm, corresponding to about 35 hexagonal units. The strand is moving from top to bottom in an applied electric potential, and each of the four DNA bases is shown in a different colour. The DNA could be sequenced by observing the flow of ions through the pore (vertical yellow shading) and recording the distinctive fluctuations of ionic current caused by each type of DNA base as it blocks the ionic flow. Alternatively, fluctuations in a transverse tunnelling current (horizontal yellow shading) carried through the graphene, and modulated by DNA passing through the pore, could be measured; the crocodile clips represent electrical connections. One possible problem is that single-stranded DNA can adhere to graphene, as shown. Three papers4,5,6 now report that fluctuations of ionic current can be measured when DNA passes through a graphene nanopore, although the resolution of the measurements is currently insufficient to detect and identify individual bases.