Dielectric spectroscopy furnishes a complex conductivity spectrum that depends on the sample's charge density and charge mobility. It can therefore provide complementary micro-structural insights to other readily available diagnostics, such as electrophoresis, electro-kinetic-sonic amplitude, and viscoelastic spectra. Here, an overview will be given on our progress using dielectric spectroscopy to help understand aqueous polymer networks and colloidal dispersions. These are convenient model systems for much more complex biological counterparts, such as extracellular matrices and tissue-culture scaffolds. This talk will review challenges from the perspective of electrokinetic modelling, focussing on the separation of bulk material properties from measurement artifacts. We will then explore applications of the theory to interpret laboratory experiments. Examples will be drawn from the literature on colloidal dispersions, and from our recent studies of polyacrylamide-based gels and ionic-surfactant micelles.