Hematopoietic cells are a group of cells that first appear in the midembryonic stage of the mouse and are essential for body growth and maintenance. For a long time, their development was widely assumed to be divided into primitive and definitive hematopoiesis. However, erythromyeloid progenitors were identified as the wave between primitive and definitive hematopoiesis, and at least three waves were recognized. An even more multilayered structure of hematopoietic development is becoming evident in recent years, with the progress and spread of lineage tracing experiments. This review will focus on recent advances in the behavior of hematopoietic stem and progenitor cells in the embryo revealed by cell lineage-tracking experiments.