A proton. It consists of three "colored" quarks,
kept together by "gluon" fields.
Special relativity is demonstrated with high speed trains.
Here you see fast trains. The red one one goes with 87% of the speed of light. It is Lorentz contracted.
The blue train is standing still. Apart from the color, the trains are identical.
Sitting in the train, you see the surroundings Lorentz-contracted. Also the blue train is short.
If you think this is contradictory, remember that simultaneity in time is perceived
differently by the different observers.
See also the older animations:
A living black hole!
The Rindler coordinate frame
I also designed the Moving Version of the University Logo (see the list
of my PhD Students)