A synthetic method of cobalt wires with platelike structure similar to Chinese caterpillar fungus (cordyceps sinensis) has been developed in aqueous media. Cobalt nanoparticles as seeds were prepared by reducing cobalt chloride with NaBH4 under inert atmosphere Which act as nucleation sites. We added an even weaker reducing agent, hydrazine, to the growth solution, and. the solution was kept undisturbed at 80 degrees C for 90 min to obtain our product. A mechanism that involved in the formation of cobalt wires has also been proposed. The discovered cobalt wires may be applied to the fabrication of nanocircuitry or ultrahigh-density storage media. (c) 2006 American Vacuum Society.