  We derive the fundamental limit to the resolution of far-field optical
imaging, and demonstrate that, while a bound to the resolution of a fundamental
nature does exit, contrary to the conventional wisdom it is neither exactly
equal to nor necessarily close to Abbe's estimate. Our approach to imaging
resolution that combines the tools from the physics of wave phenomena and the
methods of information theory, is general, and can be extended beyond optical
microscopy, to e.g. geophysical and ultrasound imaging.
