Culturing cells in three-dimensional (3D) matrices is a more accurate method of evaluating migratory properties than culturing cells on plastic (2D culture). However, 2D culture remains popular so Meyer et al. investigated which cell properties in 2D culture reflected an ability to migrate in 3D culture. Breast cancer cells cultured in 2D that had increased levels of membranous protrusions correlated with an ability to migrate in 3D culture, whereas migration in 2D culture did not.