||Haematopoiesis is a multi-stage process that involves the differentiation of multipotent stem cells and progenitor cells into distinct mature cell lineages. Here we present Haemopedia, a comprehensive atlas of murine gene expression data that covers all the mature lineages in haematopoiesis, including rare cell populations such as eosinophils, mast cells, basophils and megakaryocytes and a large collection of progenitor and stem cells. We have used this dataset to identify gene sets with specifically enriched expression in each of the mature blood cell lineages. Many of the genes in these sets show conserved lineage-enriched expression patterns in human haematopoiesis. We also identify some genes with divergent expression patterns between mouse and human, highlighting species specific differences in blood cell production. To make analyses of Haemopedia and other blood cell transcriptional datasets easier, we have created an online web portal, Haemosphere, which provides simple tools to interrogate gene expression-based relationships between haematopoietic cell types and genes of interest.