Everything in the Universe consists of both light and dark. They complement each other.
Yin is dark. It describes these qualities:
Yang is light. It comprises of these characteristics:
In particle physics and nuclear physics, particle interactions
illustrate (energy <--> mass)
Positive kaon (K+) decay in bubble chamber (source: CERN)
P Watkins' Seeing Particles exercises
History of yin-yang school of thought
where the symbol comes from.
Accelerators and Dinosaurs