Multiphoton microscopes use a femtosecond NIR laser to excite fluorescence in the sample. Excitation is performed via a multi-photon absorption process. The advantage of multiphoton excitation is that fluorescence is excited only in the focal plane, and that the laser light penetrates deep into the sample. Multiphoton excitation becomes particularly efficient in combination with non-descanned detection (NDD). This application note describes the principles of non-descanned detection in combination with the bh fluorescence lifetime imaging (FLIM) devices and shows a number of typical NDD FLIM results.