The increasing use of adaptive optics for optical sectioning microscopy techniques such as multiphoton microscopy is discussed. The multiphoton microscopy has the capability to image with potentially high resolution deeply within live samples and is very useful for clinical diagnosis. Developments regarding eliminating the limitations of the technique by producing diffraction-limited point-spread functions (PSF) and measuring aberrations of the real samples are also discussed. The modal wavefront sensing technique which uses adaptive optic element to act as a wavefront sensor and corrector in a complete imaging system is presented.