Be My Guests: For a range of applications, including medical diagnostics or drug delivery, it is necessary to encapsulate one or more components into a microcapsule. While there are many methods that can do this, most either produce a range of capsule size or are not easily scalable for making large quantities. J. Zhang et al. (p. 690 ) developed a microfluidic-based system for making capsules using host-guest chemistry. Cucurbit[8]uril, which readily forms complexes in water, was used as the host molecule and could accommodate two different guest molecules. Rapid complexation was observed of methyl viologen–modified gold nanoparticles and a naphthol-containing copolymer.