Structure of the flagellum in Chlamydomonas reinhardtii and Trypanosoma brucei. Scanning electron microscopy shows the global structure of (A) Chlamydomonas and (A’) Trypanosoma. Sections through the base reveal (B) the emergence of the two flagella from the cell wall (CW) and (B’) the single flagellum through the flagellar pocket (FP). The basal body (BB) and the transition zone (TZ) are also visible. (C,D,E,F,C’,D’,E’) Longitudinal and cross-sections through the flagellum reveal the structure of the axoneme (and of the PFR in T. brucei), and the presence of IFT trains are indicated by brackets or arrows. Scale bars: (A) 5 μm; (B) 1 μm; and (C,D,E,F) 0.1 μm. Image credit: (A,B,C,D,E,F) provided by Elisa Vannuccini and Pietro Lupetti (University of Siena, Italy). (A’,B’) reproduced with permission from Buisson and Bastin  and (C’,D’,E’) reproduced with permission from Absalon et al. . The scale bar size is indicated on each image. BB, basal body; CW, cell wall; FP, flagellar pocket; IFT, intraflagellar transport; PFR, paraflagellar rod; TZ, transition zone.