  We provide a general approach to Lipschitz regularity of solutions for a
large class of vector-valued, nonautonomous variational problems exhibiting
nonuniform ellipticity. The functionals considered here range amongst those
with unbalanced polynomial growth conditions to those with fast, exponential
type growth. The results obtained are sharp with respect to all the data
considered and yield new, optimal regularity criteria even in the classical
uniformly elliptic case. We give a classification of different types of
nonuniform ellipticity, accordingly identifying suitable conditions to get
regularity theorems.
