Heterogeneous catalysis is a core area of contemporary physical chemistry posing major fundamental and conceptual challenges, and nanoparticles are ubiquitous in many heterogeneous catalysts. It is now opportune to focus a Faraday Discussion concerning key aspects of their synthesis characterisation and use. This Faraday Discussion will explore the modern methods being used to design, synthesise and characterize nanoparticles and how these bridge across the disciplines of physical science and chemical engineering. The core aim of this discussion is to develop a fundamental understanding of these crucial aspects of catalytic science, especially relating to nanoparticle synthesis and its use in catalytic reactions, knowledge of which is essential for the design of new catalysts.