For decades, researchers have tried to cocrystallize caffeine and benzoic acid. The combination is of interest for potential pharmaceutical applications such as headache treatments. Although cocrystals have been made of caffeine with many other carboxylic acids, the benzoic acid cocrystal has remained elusive. An international team of researchers led by Dejan-Krešimir Buˇcar of the University of Cambridge and including scientists at the University of Zagreb, in Croatia; the University of Iowa; and AbbVie, a pharmaceutical research company in North Chicago, has finally succeeded (Chem. Sci. 2013, DOI: 10.1039/c3sc51419f). The researchers used computational methods to predict that caffeine and benzoic acid should form a stable cocrystal. They then prepared cocrystals of caffeine and fluorinated benzoic acids, which they used to seed cocrystallization of caffeine and benzoic acid. After they made the seed cocrystals, they obtained caffeine-benzoic acid cocrystals every time, even when they were trying to replicate the earlier negative results. The researchers suspect that the fluorinated cocrystals continued to seed crystallization even at levels too low for detection. The researchers now plan to figure out why the cocrystal was so elusive.