Our research is focussed on galactic and extragalactic compact radio sources such as supernovae, pulsars, black hole candidates, radio stars and the powerful cores of radio galaxies and quasars. With the technique of very-long-baseline interferometry (VLBI) and a network of several large radio telescopes girdling the globe, we are able to image the areas of activity of these sources and determine their positions with an angular resolution 1,000 times better than with any optical telescope on Earth.