We report on a new method to make nanostructures in aqueous solution at room temperature. We used the protein cytochrome c3 to catalyze reduction of selenate (SeO42-) to selenium Se0 by dithionite. Reduction was instantaneous. After a week spherical nanoparticles of red Se0 (about 50 nm diameter) precipitated, followed by self-assembling into crystalline nanowires, typically 1 μm long. The nanowires were composed of one strand of spherical particles; thicker strands contained several nanoparticles in parallel.