Spatiotemporal dynamics of drugs in tissues is a key determinant of their pharmacological actions. While such pharmacokinetics research has been performed at macroscopic level, those of microenvironment at cellular and subcellular scales could not have been assessed due to technical limitations. In this regard, nonlinear microscopic techniques have great potentials. With high spatiotemporal resolution provided by tissue penetrating ability of near infrared light and spatial restriction of nonlinear optical effects, multiphoton microscopy can reveal hidden phenomena inside tissues. In addition, various optical phenomena other than fluorescence can be utilized to image targets that cannot be labeled with and/or visualized by conventional fluorescence techniques. In this talk, I will introduce the basics of such imaging techniques as well as our attempts to utilize them for characterizations of pharmacokinetics as well as cellular responses in microenvironment at subcellular resolution.