 Functional photoacoustic imaging, FPAI, is a powerful tool for biological imaging with unique capabilities, including scalability, high resolution, and the ability to measure functional properties. At the nanoscale, FPAI can image the surface light absorption characteristics of materials and single organelles within cells. At the microscopic and macroscopic scale, FPAI can measure and quantify physiological parameters such as oxygen saturation, desal morphology, blood flow, and metabolism. Recent technological advancements and applications are discussed, along with potential future directions. This article was authored by Bayoli Park, Donginoh, Jesus Kim, and others.