LTi cells are part of the ILC family and essential for the formation of secondary lymph nodes within the embryo. This data set contains the analysis of lymphoid tissue (LTi) cell ontogeny, studied by expression profile analysis with RNA single cell sequencing of the fetal liver vs. embryonic periphery at embryonic stages E13.5 an E14.5. They indicate a proliferating precursor population mainly in the fetal liver, while the embryonic periphery harbors the definitive lineage. Overall design: Ontogeny of lympoid tissue (LTi) cells studied by mRNA expression analysis with single cells sequencing of the fetal liver vs. embryonic periphery at E13.5 and E14.5