  Nonlinear optics has been a very dynamic field of research with spectacular
phenomena discovered mainly after the invention of lasers. The combination of
high intensity fields with resonant systems has further enhanced the
nonlinearity with specific additional effects related to the resonances. In
this paper we review a limited range of these effects which has been studied in
the past decades using close-to-room-temperature atomic vapors as the nonlinear
resonant medium. In particular we describe four-wave mixing (4WM) and
generation of nonclassical light in atomic vapors. One-and two-mode squeezing
as well as photon correlations are discussed. Furthermore, we present some
applications for optical and quantum memories based on hot atomic vapors.
Finally, we present results on the recently developed field of quantum fluids
of light using hot atomic vapors.
