Rational design of functional molecular assemblies from food proteins such as complex coacervates constitute a way toward the development of innovative food products and ingredients. It constitutes also an opportunity to generate new protein-based materials with new functional or bioactive properties. Complex coacervation, a form of liquid-liquid phase separation, is a well-known associative process that can occur between oppositely charged bio-macromolecules. Heteroprotein complex coacervation (HPCC) constitutes a special case of such process in which the dense liquid phase is composed of interprotein complexes [1]. The formation of such intermolecular complexes leading to coacervates is influenced by many physico-chemical and structural factors such as pH, ionic strength, concentrations, protein ratio and charge density. Although complex coacervation has been studied for decades, HPCC is less well understood. I will present and discuss the identified similarities and differences with other coacervation systems, highlighting the key elements. The application of HPCC in food and non-food sectors constitutes an emerging research challenge. The potential use of HPCC for purification purposes or encapsulation and delivery of bioactive ingredients will be discussed.