Tunable resistive pulse sensing (TRPS) is an experimental technique that has been used to study and characterise colloidal particles ranging from approximately 50 nm in diameter up to the size of cells. The primary aim of this Review is to provide a guide to the characteristics and roles of TRPS in recent applied research. Relevant studies reflect both the maturation of the technique and the growing importance of submicron colloids in fields such as nanomedicine and biotechnology. TRPS analysis of extracellular vesicles is expanding particularly swiftly, while TRPS studies also extend to on-bead assays using DNA and aptamers, drug delivery particles, viruses and bacteria, food and beverages, and superparamagnetic beads. General protocols for TRPS measurement of particle size, concentration and charge have been developed, and a summary of TRPS technology and associated analysis techniques is included in this Review.