A device for pumping and compressing fluids, particularly in micro-liter quantities. First and second polarized cylindrical magnets are mounted in a cylinder with an inlet and an outlet port. The first magnet is adapted to rotate on the axis of the cylinder and has a fixed longitudinal position on that axis. The second magnet is free to move longitudinally but kept from any rotational movement, as a piston in the cylinder. The inlet port is open when the piston magnet is repelled by the rotor magnet's polarity and the outlet is open when the piston magnet is attracted by the rotor magnet's polarity as it rotates.