The special value of radio astronomy lies in the probing of extreme conditions in the universe, including the highest energies and the lowest temperatures. Radio waves can penetrate clouds of gas and dust to reveal objects in the universe and, in particular, in our Galaxy that cannot be seen by visible light. To achieve the highest resolution, radio telescopes in widely separate parts of our globe combine their reception to produce a synthesized image. This is a splendid example of international collaboration. Among the images visualized are pulsars, derived from the remnants of supernovae explosions, and quasar sources powered by black holes.