In contrast to what was believed for the first twenty years of AGN studies, the continuum spectra of AGNs are quite complex. As mentioned in Chapter 1, at least to a low-order approximation the SED of AGNs can be described as a power law of the form Fv ∝ v-α, where α is generally between zero and unity. This led to the initial suspicions that this continuum is non-thermal in origin. It is certainly tempting to attribute the bulk of an AGN spectrum to synchrotron emission, primarily because of the broadband energy characteristics of the emission and because of the similarity of the spectra to known synchrotron sources such as supernova remnants and extended radio sources. By the end of the 1970s, the best working model to produce the broad-band continuum was the synchrotron self-Compton (SSC) mechanism. Given a power-law distribution of energies, relativistic electrons in a magnetic field can produce a synchrotron power law spectrum over many decades of frequency. Moreover, it is possible in principle to produce the higher-energy emission, all the way up to X-rays, via the SSC process; the SSC process becomes important when the synchrotron radiation density becomes sufficiently high that the emitted photons are inverse-Compton scattered off the very electrons which are responsible for the synchrotron radiation. The major difficulty in understanding whether a particular source of radiation is pure synchrotron emission or SSC is that SSC-boosted photons have the same relative energy distribution as the original photons, thus providing no unique indication of the process.