Book excerpt: The growing demand for the detection of trace analytes, such as drugs, biomarkers, environmental pollutants, and explosives, in different fields including on-site healthcare monitoring, disease diagnostics, environmental monitoring, and homeland security has driven the development of high-performance sensors to tackle real-world problems. Self-assembly of nanoparticles mediated by macrocyclic molecules provides a facile method to fabricate nanosubstrates with precise interparticle spacings, leading to very strong and reproducible signals. This introductory book is designed to offer fundamental insights into the nanosensing platforms based on macrocycle-functionalised nanoparticles, including their synthesis and functionalisation, host–guest chemistry, and optical spectroscopies. It also explores potential applications of these nanosensing platforms in biological and chemical sensing.