Cell migration plays a key role in various physiological/pathological phenomena such as wound healing, cancer metastasis or embryogenesis. Until now, many studies have focused on migration on 2D substrates but less is known about migration in 3D environments. The aim of our study is precisely to analyze cancer cell migration in 3D fibrous collagen gels using reflectance confocal microscopy. Reflectance microscopy allows to simultaneously visualize the position of collagen fibers and the actin cytoskeleton of transfected cells, and thus to establish the link between the collagen fiber displacement field and the cell morphology.