Nanoparticles, Lightly Twisted: The helical structures that are widespread in natural macromolecules result from well-coordinated bonding interactions and affect their physical properties in striking ways. To obtain helical nanoparticles, Srivastava et al. (p. 1355 , published online 11 February) slowly oxidized cadmium-tellurium under visible light and assembled ribbons of nanostructure. The ribbons were persuaded to twist into helices because they were doped with cadmium sulfide nanoparticles, which underwent surface oxidation and caused localized stresses that could only be relieved by a conformational change. The pitch of the twisted ribbons that were produced could be controlled by the intensity of illumination applied. This behavior offers promise for application in the development of materials with interesting optical properties.