This study aims to evaluate if a light based technique, called Optical Breast Spectroscopy (OBS) formerly known as Transillumination Breast Spectroscopy (TiBS), can be used to detect differences in breast tissue between high- and low-risk populations and within the high-risk population between BrCa1 or 2 carriers and non-carriers. These differences may include differences in breast tissue composition and metabolism at time of enrollment into the study (possibly reflecting changes occurring in adolescence) and in the rate of breast tissue change over time (possibly reflecting rate of tissue transformation from normal to ultimately malignant state).