a, Representative spatial maps of the flow velocity of photoconverted HSPCs in the caudal vasculature at 54 h.p.f. Arrows show the direction of blood flow, and different colours indicate the level of velocity. b, Schematic illustration of how HSPCs enter the CHT via the circulation. c–e, Time-lapse imaging (c, d) and speed curve diagram (e) show that HSPCs arrive either from the intersegmental vessel (green arrow in c) or the CVP (red arrowhead in d) into the CHT and gradually decelerate (see Supplementary Video 3). Scale bar, 20 μm.