Quantifoil® carbon support film (Quantifoil MicroTools GmbH) or a 200 mesh Au TEM finder grid with a R2/2 Quantifoil® carbon support film (LFH2100AR2, AURION). (ii) Samples of either the fluorescent beads or emulsions were first diluted tenfold with buffer to control the density of oil droplets and provide more suitable conditions for cryo-TEM imaging. Then, 3 μL of the diluted samples were applied on TEM grids in an automated vitrification robot (Thermo Fisher Scientific Vitrobot™ Mark IV). Samples were blotted with a blotting time of 3 s and blot force of -4 and subsequently plunged into liquid ethane. Prior to further measurements, all vitrified samples were stored in a grid box at 77 K in a liquid nitrogen tank.