Mitochondrial intrusion sites facilitate membrane contact with the ER and other mitochondria. (A–C) Examples of ER-to-mitochondrion intrusion sites detected in (A) set #1, (B) set #2, and (C) set #3, displayed as partial (50 nm) 2D-averaged projections of raw EM and AIVE data (left panels), rendered in 3D (center panels), and with a colorimetric distance map relative to the ER (right panels). For animations of these data, see Video 8. Additional examples are provided in Fig. S6, A–C. (D and E) Examples of mitochondrion-to-mitochondrion intrusion sites detected in (D) set #1 and (E) set #2, displayed as partial (50 nm) 2D-averaged projections of raw EM and AIVE data (left panels), rendered in 3D (center panels), and with a colorimetric distance map relative to other mitochondria (right panels). For animations of these data, see Video 9. Additional examples are provided in Fig. S6, D and E. (F) 3D-rendered examples of empty intrusion sites detected in each dataset. Scale bars, 200 nm; bounding dimensions of each 3D dataset frame, 1.5 × 1.5 × 1.5 µm.