Microquasars behave like extragalactic quasars but at a reduced scale, hence their name. The compact central object (black hole) in a quasar has a typical mass of several millions that of the Sun, while the microquasar compact object is merely a few solar masses. Excluding these scale differences, the physics of both type of systems is believed to be essentially the same.
The small size of microquasars makes them specially easy to monitor
in time. Considering that the characteristic time of matter accretion onto
the compact object is proportional to its mass, the variations observed
in a microquasar in time scales of minutes (easy to follow by a human observer)
correspond to similar phenomena that would take thousands of years in a
quasar with, say, 109 solar masses.
Figure taken from Mirabel & Rodríguez, Nature 392, 673 (1998)