Fluorescence microscopy has become an essential tool in cell biology. This technique allows researchers to visualize the dynamics of tissue, cells, individual organelles, and macromolecular assemblies inside the cell. Unfortunately, fluorescence microscopy is not completely "noninvasive" as the high-intensity excitation light required for excitation of fluorophores is inherently toxic for live cells. Physiological changes induced by excessive illumination can lead to artifacts and abnormal responses. In this chapter, we review major factors that contribute to phototoxicity and discuss practical solutions for circumventing photodamage. These solutions include the proper choice of image acquisition parameters, optimization of filter sets, hardware synchronization, and the use of intelligent illumination to avoid unnecessary light exposure.