In this talk I will discuss our work on the application of optical spectroscopy to sensing and label-free imaging. A compact spectrometer is developed by using a G-Fresnel device with dual functionalities of focusing and wavelength dispersion, which can enable miniaturization of optical spectrometers and thus the integration of optical spectroscopy with smartphone technology. The use of smartphone based diffuse reflectance spectroscopy for hemoglobin sensing and for detecting plant d i s e a s e s w i l l b e d i s c u s s e d . M e r g i n g t h e c ap a b i l i t i e s o f v i b r a t i o n a l spectroscopy and holography can lead to new opportunities for bio- imaging. The vibrational response of target molecules provides a means for chemical contrast, while holographic detection captures both the amplitude and the phase of a complex signal field to enable label-free three-dimensional imaging. Vibrational spectroscopic holography, including holographic coherent anti-Stokes Raman scattering imaging and holographic sum frequency generation imaging, will be discussed.