For the first time, proposed is an ultracompact biomedical optical instrument for ultrasound tagged optical tomography that can simultaneously realize an agile ultrasonic probe and an agile optical probe, all in the same fiber-optic package, allowing close proximity in-vivo internal/intracavity imaging. In addition, the same dual probe can be used for external in-vivo imaging of several centimeters thick biological sample. The ultrasound and optical probe utilize the multiwavelength nature of light to provide a compact and fast mechanism to distribute and steer probing beams, thereby reducing motion artifacts and improving image contrast detection sensitivity.For the first time, proposed is an ultracompact biomedical optical instrument for ultrasound tagged optical tomography that can simultaneously realize an agile ultrasonic probe and an agile optical probe, all in the same fiber-optic package, allowing close proximity in-vivo internal/intracavity imaging. In addition, the same dual probe can be used for external in-vivo imaging of several centimeters thick biological sample. The ultrasound and optical probe utilize the multiwavelength nature of light to provide a compact and fast mechanism to distribute and steer probing beams, thereby reducing motion artifacts and improving image contrast detection sensitivity.