Scanning electron microscope image of a copper-nickel crystalline nanostructure. The trunk of this "nano-tree" measures only 100 nm in diameter. The leaves of the nano-tree are the result of dendritic growth of copper-nickel polycrystals starting from the top of the trunk. This nano-tree was formed by electroplating into a pore in a polymer thin film. The polymer was subsequently removed, which caused the nano-tree to fall over.