Development is driven by robust processes across scales and function. Physical description in term of physics of liquid crystals reveals as fruithfull in describing the evolution of spindle-shaped cells as myoblasts. We focus on muscle precursors to create multicellular capillary bridges and to apply forces on these nematic-like micro-tissues in 3D. The internship aims to study the creation and annihilation of topological defects in 3D tissue under mechanical constraints. These defects are known to influence differentiation, as seen in myoblast patterns and model organisms like hydra. The project involves monitoring actin filament dynamics using 2-photon microscopy, and identify differentiation patterns.