The present invention relates to systems for low-energy (e.g., 1.0 nJ-7.0 nJ) photoacoustic microscopy and methods for employing such systems. In certain embodiments, such systems employ a low-energy nanosecond pulsed laser beam (NPLB), at least two amplifiers, and a data acquisition system with at least three channels to generate at least three digital signals (e.g., which are averaged and normalized to the energy of the NPLB). In other embodiments, provided herein are systems for combined use of photoacoustic microscopy, dye-based microscopy (e.g., with fluorescein), and optical coherence tomography.