My thesis relates on the investigation of a family of inorganic nanoparticles with non-centrosymmetric crystal structure, known as harmonic nanoparticles. It treats both fundamental and application aspects. While most of the works on the nonlinear properties of micro- and nano-structures have addressed the generation of distinct signals, such as second or third harmonic, I demonstrate that the combination of harmonic nanoparticles with dual output lasers can enable the simultaneous excitation and detection of multiple emission orders, including several harmonics and signals stemming from various sum and difference frequency mixing processes. The strong optical responses remain conserved when the harmonic nanoparticles are embedded in biological media, opening the way to multi-functional applications, as shown in this thesis, such as photo-triggering, localized photo-damage and opto-poration.