 The axial resolution of the system can be improved by using a wider bandwidth ultrasound transducer as long as the bandwidth matches that of the photoacoustic signal.The lateral resolution of photoacoustic microscopy depends on the optical and acoustic foci of the system.Optical-resolution photoacoustic microscopy (OR-PAM) uses a tighter optical focus than acoustic focus, while acoustic-resolution photoacoustic microscopy (AR-PAM) uses a tighter acoustic focus than optical focus.