Reciprocal interactions between hemopoietic stromal cells and immature hemopoietic cells in human spleens obtained from 20 fetuses of 10-28 weeks gestation were observed by transmission electron microscopy and scanning electron microscopy. The close association of stromal cells with immature hemopoietic cells was confirmed under the electron microscope and a presumptive HIM （Hemopoietic inductive microenvironment） was visualized. In regions of immature hemopoietic cell-reticular cell

endothelial cell

macrophage and interdigitating cell contact

some communicating structures were found between the plasma membranes of adjacent cells; moreover

the cytoplasm of these four stromal cells were full of various kinds of organelles. These results suggest that reticular cells

endothelial cells

macrophages and interdigitating cells are component parts of the HIM of human fetal spleen and that these cells have a nurturing function in relation to hemopoietic cells.