We developed a photoacoustic imaging system that has real-time imaging capability with optical resolution. The imaging system is capable of scanning at $20\mathrm{Hz}$ over a $9\mathrm{mm}$ range and up to $40\mathrm{Hz}$ over a $1\mathrm{mm}$ scanning range. A focused laser beam provides a lateral resolution of $3.4\mathrm{\mu m}$ as measured in an optically nonscattering medium. Flows of micrometer-sized carbon particles or whole blood in a silicone tube and individual red blood cells (RBCs) in mouse ear capillaries were also imaged in real time, demonstrating the capability to image highly dynamic processes in vivo at a micrometer-scale resolution.