Hypothesis: Interfacial assembly between nanoparticles and complementary ligands can in-situ generate Janus-like particles, rendering high stability of a Pickering-based system. Hence, through the self-assembly and formation of a Janus structure at the air/water interface, which is composed of a hydrophobic particle layer in the inner air phase and then a hydrophilic polymer layer in the aqueous phase, it should be possible to fabricate ultra-stable Pickering foams. Experiments: Foams containing different highly hydrophobic particles and hydrophilic polymers or microgels were prepared, and their stability was investigated. The interfacial structure of the Pickering bubbles was examined, where a new mechanism for ultra-stable foam formation was established. The properties of the foams were further demonstrated. Findings: The interfacial co-assembly exploiting binary foam stabilizers being very hydrophobic particles and a hydrophilic polymer/particle results in the formation of ultra-stable Pickering foams. The generation of a Janus bilayer at the interface is the key factor responsible for their high stability. This strategy can be universally applied to any kind of highly hydrophobic particle with various hydrophilic polymers or colloids. The obtained foams demonstrate excellent tunability and plasticity, which could be used for mold-casting and printing. (C) 2020 Elsevier Inc. All rights reserved.