  This short review is devoted to the simple process of drying a
multi-component droplet consisting of a complex fluid containing a salt. These
processes provide a fascinating subject for study. The explanation of the rich
variety of patterns formed is not only an academic challenge, but a problem of
practical importance, as applications are growing in medical diagnosis and
improvement of coating/printing technology. The fundamental scientific problem
is the study of the mechanism of micro- and nanoparticle self-organization in
open systems. The specific fundamental problem to be solved, related to this
system is - the investigation of the mass transfer processes, the formation and
evolution of phase fronts and the identification of mechanisms of pattern
formation. The drops of liquid containing dissolved substances and suspended
particles are assumed to be drying on a horizontal solid substrate. The
chemical composition and macroscopic properties of the complex fluid, the
concentration and nature of the salt, the surface energy of the substrate and
the interaction between the fluid and substrate which determines the wetting,
all affect the final morphology of the dried film.
