  In this paper we give an overview of recent results on (upper and lower)
discrepancy estimates for (concrete) sequences in the unit-cube. In particular
we also give an overview of discrepancy estimates for certain classes of hybrid
sequences. Here by a hybrid sequence we understand an $(s+t)$-dimensional
sequence which is a combination of an $s$-dimensional sequence of a certain
type (e.g. Kronecker-, Niederreiter-, Halton-,... type) and a $t$-dimensional
sequence of another type. The analysis of the discrepancy of hybrid sequences
(and of their components) is a rather current and vivid branch of research. We
give a collection of some challenging open problems on this topic.
