Temperature-sensitive core-shell nanostructures are synthesized by functionalizing a hydroxyl-terminated dendrimer with a reversible addition-fragmentation chain transfer (RAFT) polymerization chain-transfer agent. RAFT polymerization of N-isopropylacrylamide produces a shell around the dendrimer (see Figure). In aqueous solution, changing the temperature by 10degreesC can reversibly open and close the poly (N-isopropylacrylamide) shell. Entrapment and temperature-induced liberation of pyrene from the nanostructures is demonstrated.