The Centrosome (CS) is an organelle located near the nucleus that constitutes the primary Microtubule Organization Center (MTOC) in animal cells. The distribution of the microtubule cytoskeleton is therefore determined by the localization of the CS. Localization of this organelle is important for many cellular processes: I) Cell shape and polarization[6], II) Cell migration and III) Cell cycle.The processes underlying CS localization are mechanical, with two possible scenarios: I) Pushing forces may be generated at the tips of MTs growing from the centrosome against an object such an organelle, cell cortex or plasma membrane; II) Pulling forces may be generated by MTs that remain attach to the CS and their tips shrink against an object. Alternatively, force could be generated along the length or tip of MTs by motor proteins and may be transmitted to the CS. Both pushing and pulling forces have been demonstrated to play a role in different organisms, but how the net force on the CS is regulated in order to achieve proper positioning is still an important open question.The aim of this project is to study CS positioning in HeLa cells. We will first determine if the dominant force involved in centrosome positioning is pushing or pulling and secondly, explore the different contributions of these forces. To achieve this goal, we will directly perturb the force balance on the CS by severing MTs with laser ablation.