Dynamic of the number of cells over time as the embryo grows I would like to investigate the dynamic of the number of cells over time as the embryo grows. I am interested in any multicellular animal species for which we can have some data. How does the number of cells change over time in an embryo? I welcome any graphs, empirical data and/or mathematical expression for this dynamics.

There are some interesting analyses in mice, zebrafish, and worms. These papers contain a lot of data at the single-cell resolution, so you'll need to read and find the exact numbers about cell counts over time. You might also want to take a look at this classic paper about cell counts in humans.