On Day 5 of #LMB365 we have a surface view of a Drosophila embryonic blastoderm provided by Ghislain Gillard @GhislainGillard in the group of Katja Roeper @katjaroeper in the Cell Biology Division @CellBiol_MRCLMB. During early development, the fruit fly (Drosophila melanogaster) embryo is a syncitia, meaning that it contains many nuclei in a common cytoplasm. These nuclei then migrate toward the surface of the embryo, where membranes will be built around them to form individual cells with a single nucleus, in a process termed cellularisation. This image represents an embryo after this step of cellularisation, viewed from the top. Each roundish structure corresponds to a single cell containing a single nucleus (not visible here). The membranes are stained for several proteins, one of them, Actin (in magenta) being essential for this cellularisation to occur