4,000 cells play the first movements shaping an early Drosophila embryo at gastrulation stage. The entire embryo is 500µm long and 160µm large. It is imaged during 45 minutes of development using two-photon excited fluorescence microscopy. The cell trajectories are tracked and displayed using computational analysis. The time is encoded along the cell trajectories with a color, from dark blue to green. Quantitative analyses of cell motion reveal highly organized movements and collective processes.