Progress in single-molecule spectroscopy in cells.

Time-dependent single-molecule spectroscopy allows the direct observation of molecular processes in real time, capturing transient and stochastic events that cannot be detected using conventional ensemble-averaged methods. It offers a promising approach to uncovering the physical and chemical transformations underlying cellular responses. Recent advances in the probe development, specific labeling strategies, and spectroscopy instrumentation suggest the feasibility of monitoring a single molecular machine's actions inside a living cell. 2009 Elsevier Ltd. All rights reserved.