In recent years, engineers have worked to develop molecules through a technique known as "self-assembly," where molecules join to form much larger functioning objects. Now engineers from the University of Rochester in Rochester, N.Y., have taken an important step: developing fluorescing self-assembled molecules more than 1000 times larger than previous structures. The largest of the research team's structures are 50 µm long, larger than most cells in the human body. The research team began with a type of polymer chain used in paint to keep it from sticking together and in adhesive materials. The two ends of the hybrid chain behaved very differently, and through experimentation the engineers manipulated their behavior to force them to assemble into specified shapes. The ability to incorporate hydrogen bonds into polymer structures, providing the same source of stability that aids DNA and other self-assembled proteins in arranging themselves, was important to the project's success.