  This article reviews a new and general theory of nonuniform fluids that
naturally incorporates molecular scale information into the classical van der
Waals theory of slowly varying interfaces. The method optimally combines two
standard approximations, molecular (mean) field theory to describe interface
formation and linear response (or Gaussian fluctuation) theory to describe
local structure. Accurate results have been found in many different
applications in nonuniform simple fluids and these ideas may have important
implications for the theory of hydrophobic interactions in water.
