land-ExM reveals SGs at different locations of cells. (A–C) land-ExM images of U2OS cells untreated or treated with NaAsO2 for 20 or 60 min, then immunostained with anti-G3BP1 antibody. Scale bar: 5 µm in pre-expansion unit. Linear expansion factor: 4. (D–F) land-ExM images of U2OS cells stained with mCLING (magenta) and NHS ester dye (cyan) and immunostained with anti-G3BP1 (yellow) and anti-Sec61b (white) antibodies. Cells were untreated or treated with NaAsO2 for 20 min or 60 min. Scale bar: 5 µm in pre-expansion unit. Linear expansion factor: 4. (G) Magnified images of E showing SGs formed adjacent to ER (orange arrowheads). Scale bar: 1 µm in pre-expansion unit. (H) Analysis of the number of nuclear tunnels per cell with or without 60 min NaAsO2 treatment. Each bar represents the mean ± standard error of more than 18 cells. The ns indicates P > 0.05 by Welch’s t test. (I) Analysis of the diameter of nuclear tunnels in cells with or without 60 min NaAsO2 treatment. Each bar represents the mean ± standard error of more than 20 cells. ns indicates P > 0.05 by Welch’s t test. All images were taken with an Airyscan microscope. The cell shown in F is also shown in Fig. 4, A, F, and L.