Video replicating some of the challenges neutrophils are likely to encounter along their way through tissues. Neutrophils are the white blood cells and their main function is to protect us against infections. To accomplish their mission, neutrophils have to be able to move out of the blood stream and through the tissue, following chemical signals diffusing from the site of an injury or infection. In this movie, human neutrophils move from 0 (bottom) to 100 % (up) chemoattractant concentration (100nM fMLP), through small channels. One can easily see that neutrophils can navigate without trouble around posts in the middle of these channels. Notice that neutrophils extend on both sides of the posts before the symmetry is broken and one side is favored. Also notice that most of the neutrophils resolve the challange without any delay of their migration. Channels have a cross section of 3 x 6 µm and are 160 µm long, time-lapse imaging was recorded with one frame every 10 seconds.