We report optical writing at the nanometer scale of spin coated PMMA-spiropyran films. By using a near-field optical microscope, pure optical nano-writing with a resolution of 160 nm and writing speed of 0.4 µm/s was achieved. Simultaneous topographic and optical writing was also obtained by simply coupling to the near-field few more mW of laser power. Due to the fast optical response of the spiropyran molecule, nano-lithography on PMMA-spyropyran thin films appears to be very attractive for future photonics applications.