The peripheral component interconnect (PCI) high-speed stepper motor controller introduced by Prior Scientific Inc. controls the microscope stage, joystick, focus motor, filter wheels and shutters from the user's PC, thus eliminating the need for a controller box. A 32-bit bus communicates at speeds of 133 MB/s, resulting in a response time of <250 ns. It produces a 0.01-µm step size for X- and Y-axis movement, and 0.002 µm for Z. The PCI card is CE-compliant and designed with a 32-bit DLL that is compatible with all of the company's products. The device accepts encoder input to provide positioning accuracy.