Like a Fat Globule in Milk: Why Heavy Quarks Rule Inside Mesons
A drop of cream in a glass of milk. Shake it, and the fat doesn't spread evenly: it clumps into denser blobs that move differently from the rest of the liquid. Quarks inside mesons, tiny particles that live for mere fractions of a second, behave in much the same way.
A meson consists of a quark and an antiquark, and they are rarely equals.