CD81 and breast cancer: In this work we co‐encapsulate MCF‐7 breast cancer cells and human dermal fibroblasts (HDF) in microdroplets and label them with gold nanostars (AuNSt) functionalized with distinct Raman reporters and surface coatings: poly‐l‐arginine hydrochloride (AuNSt@PA) for HDFs, and anti‐CD81 antibodies (AuNSt@AB) to track small EV release from MCF‐7 cells.