A T cell is held by a micropipette on the left hand side. A biomembrane force probe consists in a bead adhering to a red blood cell, which is maintained by a micropipette (on the right hand side) with a controlled aspiration pressure that sets the red blood cell stiffness. The T cell emits a protrusion towards the antibody coated bead and exerts mechanical forces on it. The LIFEACT-mCherry fluorescently marks polymerized actin. br DIC microscopy (left), and mCherry channel (right). Frames are taken every 4 s. Movie is played at 10 frames per second. Bar is 5µm. br Video credit: Husson J, Chemin K, Bohineust A, Hivroz C, Henry N (2011) Force Generation upon T Cell Receptor Engagement. PLoS ONE 6(5): e19680. doi:10.1371journal.pone.