Bundling of collagen fibres by a mesenchymal cell. Cells were embedded within 3D bovine collagen (1 mg/ml) and images of migrating cells were acquired by CCHM. For better visualization of the fibre bundling, a situation when the cell retracts its pseudopodium, thus relaxing the fibres, is demonstrated. Left: Whole cell image, arrow indicates the direction of cell’s movement. Scale bar: 10 μm Right: A sequence of representative images with indicated time intervals corresponding to the Suppl. Video V4. Upper and bottom row show the same images, in the bottom row the three separate fibres are marked by different colours. Several fibres are apparently clustered by the cell protrusion, and a prominent displacement of these fibres is well seen after the protrusion is retracted and the fibres return to their relaxed positions. Scale bar 5 μm. Contrast was adjusted to higher degree in the inset.