Lymph nodes and spleen are the places where adaptive immune responses are initiated against pathogens and vaccines. Various stromal cell subsets organize the intricate organ structure and promote the proper functioning. Besides endothelial cells which control lymphocyte trafficking, the major stromal cell type are the fibroblastic reticular cells (FRC) that form a three-dimensional network. They serve not only as scaffolds for dendritic cells and lymphocytes but are also important for lymphocyte homeostasis, and the regulation of adaptive immunity. During my presentation I will highlight the interesting structure and function of these FRC networks in homeostasis and immunity. In addition, new results will be presented on the heterogeneity of these FRC along with the various niches that they form, thereby allowing the development, survival and function of distinct lymphocyte subsets.