When water molecules (red and white) and sodium and chlorine ions (green and purple) in saltwater (shown at the right) encounter a sheet of graphene (pale blue, center) perforated by holes of the right size, the water passes through (on the left), but the sodium and chlorine of the salt are blocked.

Full resolution (368 × 220)
When water molecules (red and white) and sodium and chlorine ions (green and purple) in saltwater (shown at the right) encounter a sheet of graphene (pale blue, center) perforated by holes of the right size, the water passes through (on the left), but the sodium and chlorine of the salt are blocked.