The enriched multistep paradigm for leukocyte extravasation. Progressive stages of leukocyte-endothelial interaction lead to diapedesis. Given new findings by Schreiber et al and other recent publications,^4,5  steps 4 and 5 were added to the canonical paradigm.¹  Apical and abluminal chemokines are shown to exert distinct functions. Shear forces of flowing blood are integrated into the scheme as promoting certain stages of the process, rather than being sheerly disruptive. Illustration by A. Y. Chen.