Water transport can drastically change under different conditions and can even achieve superlubricity, meaning that friction virtually vanishes. The microscopic origin of this counterintuitive property is unclear. Using a cryogenic atomic force microscopy technique, Wu et al. directly imaged bilayer hexagonal two-dimensional water islands on homopolar graphene and heteropolar hexagonal boron nitride monolayers and measured their friction forces as a function of island area. The experimental data confirmed a frictionless limit for water islands transport on graphene and, together with molecular dynamics simulations, demonstrated that this property originates from a delicate interplay between the water-water and water-surface interactions. —Yury Suleymanov Water transport in low-dimensional materials for nanofluidic devices has recently attracted tremendous attention ( 1– 14). The key interest lies in that the water flow rate could be drastically enhanced when the dimension of the confinement geometry approaches the atomic scale (<1 nm), leading to almost vanishing friction (superlubricity) ( 1– 6). This counterintuitive property has potentially broad applications in desalination ( 15– 17), nanofiltration ( 6, 11, 18), and energy harvesting ( 19, 20). The frictionless water transport is best exemplified in the homopolar carbon-based nanomaterials, such as zero-dimensional (0D) nanopores ( 15, 16), 1D carbon nanotubes ( 1– 5, 11), and 2D channels ( 10, 12) made from graphene layers. It has been proposed that the superlubricity may arise from the curvature-induced structural incommensurability for the water in 1D carbon nanotubes ( 21). However, this idea cannot apply to the 2D graphene channels, where no curvature effect is present. So far, our understanding of the frictionless water transport under atomic confinement is still elusive.