Comment by ClaraForm

Other commenters are wrong. Live-cell can be done with older single-molecule localization microscopy using techniques like PAINT. The fluorophore is usually strategically added in a way that binding-unbinding events cause excitation. Algorithms can then infer identity of single fluorophores based on their excitation pattern/strength and can predict whether it's two distinct fluorophore molecules or the same molecule moving over multiple frames of image acquisition.