A method and apparatus for assessing bone tissue comprises the steps of and means for: exposing a sample to nonionizing radiation; detecting nonionizing radiation after transit in the bone tissue; measuring optical properties from the detected nonionizing radiation to characterize bone tissue across an entire selected spectral range using a continuous wave model, a frequency domain model or a combination of both wave model and frequency domain models; and determining composition, structure, physiology or a combination thereof of bone tissue from the measured optical properties.