This course covers fundamentals and recent advances in in-vivo near-infrared (NIR) spectroscopy and imaging of deep biological tissues. The course reviews physical and physiological background of light transport in tissues: absorption and scattering of light, optical properties of tissues and related physiological quantities such as concentrations of fat, water and hemoglobin. The background also includes physical principles of quantitative spectroscopy and imaging and is followed by the discussion of the design of the near-infrared time-domain, frequency-domain, continuous wave, and optoacoustic systems for spectroscopic and imaging applications in deep tissues. The course concentrates on the human applications of the spectroscopic and imaging NIR techniques. Spectroscopic applications reviewed include bone marrow, peripheral vascular disease and sleep apnea studies. NIR imaging applications in neonatal brain imaging, functional brain activity studies, and mammography are included. Applications of NIR imaging in combination with MRI are also considered. The practical demonstration of a Near Infrared Tissue Oximeter (ISS, Champaign IL) will teach you how to measure hemoglobin concentration in tissues.