When a material is under stress, it tends to relax. Relaxation elicits alterations in material mechanical properties, which can result in instability. The aim of this thesis is to understand a specific mechanical failure known as syneresis, i.e. the contraction of the material accompanied by the expulsion of fluid. Syneresis is a typical mechanical instability mostly encountered in food products which are colloid-based soft solids. In this thesis we explore the underlying physics governing syneresis in colloidal materials via investigating constituent particle dynamics at multiple length scales. In order to do so, we extract the problems to their basic elements and design model food systems, and more fundamental colloid- based models to study the dynamics during syneresis in detail and provide new fundamental insights.