VLBI measurement of quasars
	Since 1992, Very Long Baseline Interferometry observations at 3mm wavelength are regularly made with an array of 3-4 European radio telescopes (including the IRAM 30m telescope) and 5-6 American radio telescopes. These observations provide the highest spatial resolution of ~100 micro-arcseconds. This allows a detailed view of the center region of active galaxies (at cosmological distances) with energetic jet-like outflows powered by a black hole.