The behaviour of water in nanopores is very different from that of bulk water. For example, water can spontaneously evaporate if it is confined in a sufficiently narrow hydrophobic nanopore. Now IGERT-LifeChips faculty members Zuzanna Siwy and Kenneth Shea with co-workers have shown that a single hydrophobic nanopore in a PET membrane can undergo reversible wetting and dewetting under the influence of an applied electric field, as predicted by molecular dynamics simulations. The nanopores are made hydrophobic by treating them with (trimethylsilyl)diazomethane. The cover is a photograph of a water droplet (which measures approximately 2 mm across) on a PET surface that has been treated in this way to make it hydrophobic.