Real-time imaging reveals dynamic endolysosomal trafficking events. (A and B) Time-lapse imaging of 3-d-old SC>CD63-GFP males stained with LysoTracker red. (A) An mMVBL containing ILVs (asterisks) fuses with a large nonacidic SV (arrowheads; Video 1). Approximate outline of SC is marked. (B) A CD63-GFP–marked protrusion invaginates from the mMVBL membrane (arrows; 0 s) and seems to form a CD63-GFP–positive punctum in the next frame. Later, a line of peripheral acidic microdomains is seen below (48.9 s; see also Video 2). Bars, 5 µm.