(A) Representative phase contrast images of cells migrating through channels with widths of 20–2 μm. Cells are able to protrude into the channels irrespective of their width. (B) Maximum intensity projections of a cell migrating through a 10 μm-width microchannel. GFP-H2KB, RFP-lifeact, and reflection are shown in green, red, and grayscale, respectively. Scale bar: 10 μm. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)