In this talk, we will present our recent developments in the context of Personalized functional Near Infra-Red Spectroscopy (fNIRS) investigations, which consist in optimizing placement of fNIRS sources and detectors on the head of the participant in order to maximize fNIRS sensitivity to some targeted brain regions, while allowing accurate local 3D reconstructions of fluctuations of oxy-hemoglobin and deoxy-hemoglobin along the cortical surface. Personalized fNIRS investigations could be combined with other modalities, whereas gluing sensors to their optimal positions allows prolonged acquisitions (whole night). We will present applications of the proposed methodology in the context of simultaneous fNIRS/TMS protocol to monitor changes in cortical excitability and in the context of whole night EEG/fNIRS monitoring to investigate sleep in physiological and pathological (epilepsy) conditions.