A structure. The structure includes a substrate, a resistive/reflective region on the substrate, and a light source/light detecting and/or a sens-amp circuit configured to ascertain a reflectance and/or resistance change in the resistive/reflective region. The resistive/reflective region includes a material having a characteristic of the material's reflectance and/or resistance being changed due to a phase change in the material. The resistive/reflective region is configured to respond, to an electric current through the resistive/reflective region and/or a laser beam projected on the resistive/reflective region, by the phase change in the material which causes a reflectance and/resistance change in the resistive/reflective region from a first reflectance and/or resistance value to a second reflectance and/or resistance value different from the first reflectance and/or resistance value.