Advances in Proximity Ligation in situ Hybridization (PLISH) Understanding tissues in the context of development, maintenance and disease requires determining the molecular profiles of individual cells within their native in vivo spatial context. We developed a Proximity Ligation in situ Hybridization technology (PLISH) that enables quantitative measurement of single cell gene expression in intact tissues, which we have now updated. By recording spatial information for every profiled cell, PLISH enables retrospective mapping of distinct cell classes and inference of their in vivo interactions. PLISH has high sensitivity, specificity and signal to noise ratio. It is also rapid, scalable, and does not require expertise in molecular biology so it can be easily adopted by basic and clinical researchers.