  The role of tidal shear in the formation of structure in the Universe is
explored. To illustrate the possible and sometimes dramatic impact of tidal
fields we focus on the evolution of voids. We firstly analyze the role of tidal
fields both in the highly symmetric situation of an initially homogeneous
ellipsoidal underdensity embedded in an artificially imposed tidal field. In
addition, we present selfconsistent case studies consisting of N-body
simulations that start from constrained Gaussian initial conditions in which
the matter distribution is appropriately sculpted to yield an a priori
specified tidal field. We conclude that voids may indeed be induced to
collapse. Also, we present evidence for the strong relation between tidal
fields and filaments in the mass distribution.
