We proposed to use optoacoustics (photoacoustics) for biomedical applications and for more than 25 years have been working on it. In this overview we present our major biomedical optoacoustics achievements over these years. Optoacoustic diagnostic modality is based on thermoelastic generation of optoacoustic waves and combines high optical contrast and ultrasound spatial resolution. We proposed to use the optoacoustic technique for a number of applications including cancer detection in breast, prostate, and other organs; hematoma detection and characterization; monitoring of thermotherapy (hyperthermia, coagulation, freezing); monitoring of cerebral blood oxygenation in adults, neonatal patients, fetuses during late stage labor; monitoring of central venous oxygenation and total hemoglobin concentration. In early 90s we started from ideas, basic science, and first in vitro studies. In mid 90s we demonstrated optoacousitc wave: 1) detection from tissues at cm-depths (well beyond the light diffusion limit); 2) detection from microscopic tissue volumes; 3) diffraction and attenuation effects in tissues. Then we reconstructed first optoacoustic images of tissue phantoms and tissues. We developed optoacoustic methods and systems (including highly-compact laser diode systems) for monitoring, mapping, and imaging in many organs (including the human brain) and tested them in small and large animal studies and in clinical studies in healthy volunteers and patients with traumatic brain injury, circulatory shock, and anemia as well as in neonatal and fetal patients. Recently, we proposed to use optoacoustic therapy and theranostics and tested them in animal studies. At present, biomedical optoacoustics is an emerging diagnostic imaging modality with a great potential to become an invaluable tool for diagnostics, therapy, and theranostics.