  After 25 years of its existence, inflationary theory gradually becomes the
standard cosmological paradigm. However, we still do not know which of the many
versions of inflationary cosmology will be favored by the future observational
data. Moreover, it may be quite nontrivial to obtain a natural realization of
inflationary theory in the context of the ever changing theory of all
fundamental interactions. In this paper I will describe the history and the
present status of inflationary cosmology, including recent attempts to
implement inflation in the context of string theory.
