We propose a newt ype of finite domain variables, which allow any kind of compound terms in their domain. A compound term in the domain may contain unbound variables which can also become domain variables, leading to nested domain variables.With nested domain variables, we can represent the Cartesian product of several domains as a tree structure. That is, disjunctive constraints stores can be constructed as a nested domain. The consistency of a nested domain can then be checked simultaneously by different parts of computations. Two forms of lookahead are used to perform the consistency checking: deep lookahead and shallow lookahead. It is hoped that, with our lookahead techniques and nested domains, many unnecessary or-branches can be pruned at an early stage. We have tested our ideas by an experimental implementation under SICStus Prolog, and obtained very encouraging results.