Try to see a single electron. A microscope using visible light shows a fuzzy blob about 400nm in diameter. Each photon that hits the electron gives it a kick of about 1eV/c which sends it off at about 10⁴ m/s.

Try harder. Use an X-ray microscope with 0.4nm wavelength. Now you "see" a blob about 0.4nm in diameter but each X-ray photon gives the electron a kick of about 1000eV/c which corresponds to sending it in an unpredictable direction at about 10⁷ m/s.

The more you know about where the electron is, the less you know about how fast it is moving.

Examples --- What this is an example of

---