There is an old saying;"We see; yet we are blind"
Here is one of my favorite examples::Planck's Radiation LAW.
I will not publish it here-you can Google its formula.
This law led to the development of Quantum Mechanics
The law states every pieces of mass living or non living radiates photons and the frequencies of the photons are determined only by the temperature of the person or object (emitter).
It is that simple in it's meaning and allows exact calculations of the frequencies/energies of the photons!
A practical trivial application: When a thermometer states that you have a 100 Fdegree you feel ill because you are emitting more photons of energy than you are absorbing at 98.6 F and your metabolism is changing in response to whatever caused the illness.