Inflation.

A short review of inflation is given, starting with a description of the underlying mechanism and the scenario of events. Four variations--old inflation, new inflation, chaotic inflation, and extended inflation--are discussed. It is claimed that the inflationary model provides a plausible explanation for (i) the large number of particles in the universe, (ii) the Hubble expansion, (iii) the large-scale uniformity of the universe, (iv) the nearness of the universe to a critical density, (v) the absence of magnetic monopoles, and (vi) the scale-invariant spectrum of microwave background fluctuations observed by COBE (Cosmic Background Explorer). Finally, it is argued that the plausibility of inflation is enhanced by the fact that inflation is eternal.