their whole length. The length of PM-associated NCs was 707 nm ( Figure 2B , Table 2 ), the same as that of cytoplasmic NCs. Viral budding structures localized predominantly to filopodia-like protrusions of infected cells, in agreement with previous data [23] . They appeared as filamentous finger-like extensions emerging either from the tip or the sides of filopodia-like protrusions ( Figure 2C -E). Each bud accommodated a rod-shaped NC that was surrounded by densely stained material and had the same length as intracellular and PM-associated NCs ( Table 2) . Of the budding structures reconstructed in 3D, 13% appeared as extrusion intermediates (Table 2) . These structures contained a full length NC (729 nm) that was only partially extruded ( Figure 2C ): one end of the NC was tightly wrapped on all sides by the PM, whereas the other was attached to the PM along one side ( Figure 2C ). The majority (87%) of budding structures had the NC completely inserted into the finger-like membrane extension ( Figure 2D , E). Scission at the base of these fully extruded buds would lead to the release of filamentous virions ( Figure 2F and Video S1).