Cover Photograph: Hippo signaling controls cell fates in preimplantation mouse embryos. Slightly different mechanisms operate in regulation of Hippo signaling between 16‐cell stage and early blastocyst stage with more than 32 cells. Panels show the confocal images of the 16‐cell (left panel) and early blastocyst (right panel) stage embryos stained with phosphorylated Ezrin/Radixin/Moesin (magenta), a marker for apical domain and cell polarization, and the Hippo pathway coactivator Yap (green). In the early blastocysts, cell position regulates cell polarization through the Par‐aPKC system, and cell polarity controls Hippo signaling. Therefore, all the outer cells are polarized and exhibit nuclear Yap. In contrast, at the 16‐cell stage, Par‐aPKC‐independent mechanism and asymmetric cell division are also involved in regulation of cell polarization. Therefore, some outer cells are apolar and show cytoplasmic Yap.