  This contribution gives an overview on primordial non-Gaussianities from a
theoretical perspective. After presenting a general formalism to describe
nonlinear cosmological perturbations, several classes of models, illustrated
with examples, are discussed: multi-field inflation with non-standard
Lagrangians, modulaton fields, curvaton fields. In the latter case, a special
emphasis is put on the isocurvature perturbations, which could leave a specific
signature in non-Gaussianities.
