Thin tubular/linear structures connect the IM and ER in the late phase of receptor-mediated mitophagy. DRP1 KO HeLa cells were treated with DFP for 16 h and fixed with a mixture of aldehyde and osmium solutions for electron tomography. EM images of 102 serial sections (∼6-nm thickness) were reconstructed from two resin-embedded sections (300-nm thick each). (A–C) Representative EM image of section 79 (A) and its color-segmented 3D version (B) with ∼180° rotation (C), as indicated by the arrow. See also Video 3. (D and F) Rotated images of the boxed areas in B and C, respectively. (E and G) Representative EM images of the areas corresponding to D and F, respectively, in the indicated section(s) numbers. See also Videos 4 and 5. mt, mitochondria (pink); IM (green); TL, tubular/linear structures (cyan); ER (blue). Arrows in A, E, and G indicate IM. Colored arrowheads in D and F indicate tubular/linear structures, which correspond to the same-colored arrowheads in E and G, respectively. Scale bars: 200 nm (A) and 100 nm (D–G).