How do Tao and Yin/Yang relate?

Tao encompasses everything. All things you can see and all things you can’t see. This includes Energy and matter in the universe, but also the effects of things on eachother.

Yin and Yang are the concept of the effects everything in the universe has on itself and one another.

Tao can be perceived in the the working of Yin and Yang. Meaning, you can see that which is and which is not, through observing movement, existing objects and forces at work. Like Newton found gravity, though not visible, there are many more forces we find out are in action. That is the way the universe works, as such the concept Tao is meant, both in physical and cognitive.

‘Thus, constantly without desire, one observes its essence
Constantly with desire, one observes its manifestations’

Tao Te Ching – Translation taoism.net – Derek Lin