  Spectral inversion techniques based on the cloud model are extremely useful
for the study of properties and dynamics of various chromospheric cloud-like
structures. Several inversion techniques are reviewed based on simple (constant
source function) and more elaborated cloud models, as well as on grids of
synthetic line profiles produced for a wide range of physical parameters by
different NLTE codes. Several examples are shown of how such techniques can be
used in different chromospheric lines, for the study of structures of the quiet
chromosphere, such as mottles/spicules, as well as for active region structures
such as fibrils, arch filament systems (AFS), filaments and flares.
