Pulsars are among the most exotic celestial bodies known. They have diameters of about 20 kilometers, but at the same time roughly the mass of our Sun. A sugar-cube sized piece of its ultra-compact matter on the Earth would weigh hundreds of millions of tons. A sub-class of them, known as millisecond pulsars, are strongly magnetized old neutron stars in binary systems which have been spun up to high rotational frequencies by accumulating mass and angular momentum from a companion star. Today we know of about 200 such pulsars with spin periods between 1.4 to 10 milliseconds. These were first discovered in 1982 and are located in both the Galactic Disk and in Globular Clusters.