DNA’s ability to selectively bind to complementary sequences can be used to program the formation of materials through the self-assembly of DNA-functionalized particles. Research by physicist Paul M. Chaikin and chemist Nadrian C. Seeman of New York University and coworkers now shows that “multiflavored” particles, where each flavor is a different DNA sequence, can bind with many other particles to make complex materials (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1207356109). The team used a computational approach to find the practical limit of different flavors that can be on a single particle. They determined that a 2-μm colloidal particle can handle up to 40 flavors. The upper limit of DNA flavors on a single particle is dictated both by entropy costs and by the number of unique sequences that avoid nonspecific binding. Any sequences with overlaps of five or more base pairs, which could bind sequences other than their intended partner, can’t be used. For the 11-base-pair sequences that the NYU researchers use, such a rule leaves a maximum of 73 available flavors out of more than 4 million possible sequences.