Illustration of cell division in 3D fibrous matrices. (A) As the cell rounds to divide, its main protrusions thin but stay intact, and a void is created between the cell and matrix (B). The cell divides along the direction of the protrusions while exerting minimal traction around the cell body but applying high traction at the tips of the protrusions. Daughter cells fill the matrix void space (C), and respread into the matrix along the long axis of the protrusions while exerting substantial traction (D).