Biology
Cell Membrane Structure
Quick fact
The cell membrane is only about 7.5 nanometers thick, yet it contains millions of moving molecules that rearrange themselves thousands of times per second.
Why this is interesting
Your body is made of trillions of cells, each sealed by a thin, oily film that decides what gets in and out—like a bouncer at a club. But how does this film, just nanometers thick, manage to be both a fortress and a gateway?