We develop sonic-speed photoacoustic tomography (PAT) to peer deep into biologicaltissue. PAT offers functional, metabolic, molecular, and histologic imagingacross scales from organelles to entire organisms. We also develop light-speedcompressed ultrafast photography (CUP), which records up to 219 trillion framesper second, far exceeding the capabilities of commercially available cameras.CUP can capture real-time images of the fastest phenomena in nature, such aslight propagation, and can be slowed down to record slower events, such asneural conduction. In parallel, we explore quantum imaging and quantum physics.PAT physically couples pulsed optical excitation with ultrasonic detection.Conventional high-resolution optical imaging of scattering tissue is confinedto depths within the optical diffusion limit (~1 mm). PAT overcomes this limit,providing centimeter-scale penetration with high ultrasonic resolution and highoptical contrast by sensing molecules. Its broad applications include earlycancer detection and brain imaging. With a single exposure, CUP can imagetransient events on time scales as short as tens of femtoseconds. Liketraditional photography, CUP is receive-only and does not require specializedactive illumination, unlike many other single-shot ultrafast imagers. CUP canbe coupled to front-end optics ranging from microscopes to telescopes, enablingwidespread applications in both fundamental and applied sciences, from biologyto astrophysics and cosmology. We study quantum entanglement, quantum imaging,and atomic physics. Unlike classical optical imaging, quantum imaging hasachieved super-resolution beyond the diffraction limit through coincidencedetection. Because photons originate from atoms and molecules, we also investigateatomic physics at the interface between classical and quantum descriptions. Forexample, we found, perhaps surprisingly, that the Bloch equation,conventionally regarded as classical, yields the von Neumann and Schrödingerequations. We also developed a theory that models the multistage Stern–Gerlachexperiment suggested by Heisenberg and Einstein more accurately than existingtreatments.