sentence1: More advanced research has included harmonic techniques such as Multiphoton microscopy , Second-optical imaging microscopy , Photoacoustic tomography , nonlinear Raman spectroscopy , and diffuse optical spectroscopy .
sentence2: More advanced research included optical techniques such as multiphoton microscopy , secondharmonic imaging microscopy , photoacoustic tomography , nonlinear raman spectroscopy , and diffuse optical spectroscopy .