Electron micrographs of invadopodia. (A) Mature invadopodia in MDA-MB-231. (A′) The same invadopodia in which the cytoskeleton networks were color coded: microtubules in orange, intermediate filaments in blue, and actin in light/dark yellow. The majority of the actin filaments are randomly arranged so that only short pieces or cross sections are seen in a thin section (light yellow). Bifurcation of actin bundle at the tip of the invadopodia (dark yellow) is shown. Images on the right are a higher magnification of the corresponding boxed regions in A′. Red indicates the base/central part of mature invadopodia; green indicates the central/tip part of mature invadopodia. c, cell; f, filter; m, Matrigel. Bars: (A and A′ [left]) 0.5 µm; (A′, right) 0.25 µm.