With computational tools, chemists have designed a protein that self-assembles in three dimensions to produce protein crystals with the symmetry properties of their choice (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1112595109). This achievement could someday have applications in designing nanoscale materials and might also help structural biologists decide which sections of a protein to modify for coaxing crystal formation. Jeffery G. Saven at the University of Pennsylvania; William F. DeGrado of the University of California, San Francisco; and coworkers set out to design a crystal with the honeycomb-like symmetry of the P6 space group, which occurs in just 0.1% of protein crystal structures. Starting with a three-helix bundle protein, they estimated the energetic consequences of varying each amino acid that might be involved with protein-protein contacts in a crystal. From those myriad possibilities, they picked five protein sequences that were predicted to form stable crystals in the lab. One of the five, a protein called P6-d, crystallized into a structure consistent with the P6 space group. The team plans to test the technique on more complex proteins soon.