The apicosome has features of the cellular exterior. (A and B) TEM images of single H9 cells grown under feeder-free conditions on a Geltrex-coated Thermanox substrate (A) or on a tissue culture plate (B) for 20 h. (B-i) Magnified image of the boxed region in B, showing a primary cilium within the apicosome. (C) Fluorescent confocal image of a single H9 cell stained with ciliary (ARL13B) and centrosomal (γ-TUBULIN) markers as well as HOECHST (blue). (D) H9 cell expressing EZRIN–EGFP (top), stained with ER-Tracker (red); isolated H9 cell stained with Fluo-3-AM (bottom, green) and ER-Tracker (red). (E) H9 cells expressing m-TdTomato (top) or Lifeact–mCherry (bottom), stained with Fluo-3-AM. (F) Schematic of an isolated hPSC with an internal apicosome, containing microvilli (green protrusions), a primary cilium (red), and accumulated Ca²⁺. Bars: (A and B) 5 µm; (B-i) 500 nm; (C and E) 10 µm.