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The importance of the phase transformations of water cannot be overstated. The steam engine was a leap in engineering as well as a major inspiration for thermodynamics. Cloud seeding using silver iodide is arguably one starting point of crystal engineering. On page 454 of this issue, Hanikel et al. tackle the goal of harvesting water from desert air using water-catching channels inside porous metalorganic frameworks (MOFs). This technique may become important as fresh, potable water is turning scarce in many regions. The authors’ design was guided by single-crystal x-ray diffraction studies of water assembly, molecule by molecule, inside a prototype MOF. This MOF was then tuned at the atomic level to achieve better water-harvesting properties.