New techniques in far-field fluorescence microscopy have improved optical resolution down to several times the diffraction limit. The resolution currently achieved with these techniques is 28nm. Recently it was proposed that fluorescent reversible molecular compounds ("photoswitches") could be utilized in fluorescence microscopy, allowing, in principle, to improve the resolution up to molecular dimensions, i.e. 1-5nm. The use of these photochromic compounds should enable the utilization of very low light intensities, thus making the technique particularly suitable for biological applications.It is proposed to investigate the feasibility and performance of photochromic fluorescent compounds in modern far-field fluorescent microscopy techniques, as well as explore its different potential uses and applications. The aim of this project is to improve resolution to a few nanometres and, in particular, apply the technique to live-cell imaging as well as to memory storage and lithography. Undertaking this scientific project in a field's leader's laboratory will give me the opportunity to learn advanced microscopy techniques, and acquire a significant experience and expertise in the field. After having completed my training in Germany, I will be prepared to set up a research team and start an independent research career in my home country, Argentina.