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Since the popularization of nanotechnology almost two decades ago, the public has been fascinated by the prospect of a “nano-assembler” for the construction of complex three-dimensional (3D) objects. Such a device would assemble objects atom-by-atom or molecule-by-molecule. Indeed, small objects have been assembled on a 2D surface by picking up individual atoms and molecules with the tip of a scanning tunneling microscope or an atomic force microscope, respectively (1, 2). However, it is not only the action of gripping an object that presents a challenge, but also its release at the designated position. The Nobel laureate Richard Smalley described this as a problem of “sticky fingers” (3). There is, however, an alternative approach for bottom-up assembly on the nanometer scale that originates from colloidal chemistry. On page 1377 of this issue, González et al. (4) report on the synthesis of complex 3D colloidal nanoparticles, a route that may circumvent the problem of the sticky nano-finger.