In 1918, the American astronomer Heber Curtis used the Crossley Reflector at Lick Observatory in California to take optical photographs of nearby galaxies. When observing M87, the central elliptical galaxy in the Virgo galaxy cluster 53 million light years from the Sun, Curtis noted the lack of a spiral structure and observed a “curious straight ray … apparently connected with the nucleus by a thin line of matter”. This measurement heralded the discovery of radio jets, the ejection of highly collimated, relativistic plasma streams or “blobs”, from a central energy source. Forty years later radio astronomers in the UK and Australia discovered a new class of “radio stars” not obviously connected with bright optical nebulae. Caltech astronomer Maarten Schmidt then used the large 5 m Hale telescope on Palomar to identify a faint, compact optical nebula associated with one of these radio stars, 3C273. Schmidt interpreted the substantial (16%) redshift of all spectral lines in the optical spectrum as being caused by the expansion of the Universe. If so, 3C273 must be 2.4 billion light years from us, 45 times further away than M87, and the optical luminosity of the faint compact speck would have to be about one thousand times greater than the 100 billion stars of our Milky Way. Thus began the subject of quasars, quasi-stellar radio sources. Many quasars and other somewhat less spectacular “active galactic nuclei” (AGN) exhibit powerful radio jets.