We proposed biomedical optoacoustics/photoacoustics more than 25 years ago and developed this technology for imaging, monitoring, and sensing applications [1-35]. Optoacoustic diagnostic modality is based on thermoelastic generation of optoacoustic waves and combines high optical contrast and ultrasound spatial resolution. We developed optoacoustic systems (including highly-compact, multi-wavelength, fibercoupled, FDA-compliant laser diode systems) with fiber-optic, ultra-sensitive, wide-band optoacoustic probes. We tested them in small and large animal studies and in clinical studies in healthy volunteers and patients with traumatic brain injury and circulatory shock as well as in neonatal and fetal patients. The high sensitivity and bandwidth of the fiber-optic optoacoustic probes allowed for: 1) signal detection from tissues at depths well beyond the optical diffusion limit (up to several centimeters); 2) detection of microscopic tissue volumes; 3) optoacoustic imaging in large tissue phantoms and tissues with high resolution; 4) monitoring of tissue thermotherapy; 5) noninvasive probing of cerebral tissues in large animals and in humans (both neonates and adults); 6) accurate oxygenation measurements in humans in tissues and in specific blood vessels; and 7) optoacoustic waves therapeutic effects that can be used for noninvasive optoacoustic theranostics. The obtained data indicated that the systems were capable of optoacoustic measurements and mapping of cerebral blood oxygenation in adults and in neonates, detection of intracranial hematomas, oxygenation measurements both from cerebral and central blood vessels and from cerebral tissues.