The invention relates to an ultrasound head (2), to a medical observation device (1) and to a method for observing live biological tissue (4). In order to provide the surgeon with a means of quickly gaining information on sub-surface structure in the surgical area during the operation, the method comprises the steps of contacting the tissue (4) with an ultrasound head (2) and recording ultrasound data (36) and optical image data (34) through the ultrasound head (2). The ultrasound head (2) comprises a sensor side (6) for contacting the tissue (4) and an ultrasound receiver (10). The sensor side (6) is at least sectionwise optically transparent so that light may enter the ultrasound head (2).
