English: This is a blastula-stage sea urchin embryo. In turquoise we see the membranes of dividing cells, in red the microtubules of the mitotic spindle that act as "ropes" to pull the chromosomes, and in green the DNA in the form of chromosomes. To manage various vital functions, each organ is protected by an epithelium, whose architecture is essential for its barrier function. Cell division and its precise orientation are essential for maintaining the integrity of these tissues. Dysregulation of cell division orientation is linked to the emergence of epithelial cancers. There are many players involved in regulating orientation: microtubules, cell shape and several membrane proteins. But how all these players work together remains a mystery. To study the orientation of division in epithelia, I use an atypical model: the blastula of the sea urchin embryo. This project provides new tools for studying cell division, with numerous implications for the biology of epithelial cancers. The technology employed is confocal microscopy. Model LSM980 in AiryScan mode. x63Oil objective. Image subsequently colored with Fiji.