ABSTRACT Understanding how immune-heterogeneity leverages cellular diversity to achieve the adaptivity and flexibility in immune-responses is a core challenge that has not been well studied, largely due to the lack of a valid immunity tissue model for investigation of cellular communications. Recent discovery of trafficking vesicles since 2013 Nobel Prize of Medicine shined the light on the new avenue for understanding long-distance, non-contact cellular communications in modulating immunity. However, the study of such diverse and nano-sized vesicles, namely exosomes, is extremely challenging, due to immense difficulties in differentiating dynamic and heterogeneous vesicle populations presented in the in vivo system. Our research work addresses key technology gaps by developing a series of tool sets, including high-efficient and high-throughput microfluidic approach for exosome isolation, subtyping, molecular engineering and transfection, and nano-delivery. Recently, we observed that molecular packaging of secreted exosomes is highly variable upon the change of cellular culture environment as well as surrounding community. The in vitro investigations with 2D cell culture systems are incapable of interpreting in vivo exosome immunity modulation mechanism. We hypothesize that a 3D biomimetic lymph node tissue system could serve as the in vivo -like tissue model for effectively studying in vivo exosome molecular packaging and secretion dynamics upon stimulations, for interconnecting exosomal cargoes with cellular level responses. This five-year study will focus on three key challenges for precisely elucidating immune-modulation at the molecular level via the exosome route: 1) Develop a 3D, programmable biomimetic lymph node tissue foundry with well-defined immunological adaptations for mimicking in vivo immune tissue microenvironment; 2) Develop a single cell single exosome study approach for highly sensitive detection and subtyping of single exosome populations with dynamic and statistical significance for understanding immunity heterogeneity; 3) Discover motifs that can selectively pack immuno-stimulating microRNAs, as well as the MHC-binding peptides into exosomes for targeted immunity modulation, which can establish the interconnection of cargo internalization with cellular level responses. The long-term goal is to advance our understanding in immunity regulation heterogeneity and eventually be able to precisely programme immune responses at the molecular precision.