This project main objectives were to develop and set-up a complete workflow for live-cell single-molecule PAINT imaging of PD-L1 in circulating tumour cells (CTC) derived from patients as a novel diagnostic tool. This includes from the imaging probe design and labelling, isolate and capture of CTCs from liquid biopsies and analysis of the single-molecule tracking data. This project aimed at bringing an advanced microscopy technique from the laboratory setting to a useful diagnostic tool for clinics. This is very important and timing. Many new microscopy methods are entering the arena but they re generally too complex, not validated and not standardised to be used in a clinical setting. Among them super-resolution and single molecule microscopy proved to be powerful methods in the research settings but they are currently not applied in clinical setting. Super-resolution can provide imaging with high sensitivity, spatial resolution and dynamic analysis (study molecular mobility), all useful information in the clinical setting. This projects aims to provide a proof of concept of this advanced technique in the diagnostic setting.