The concept of yin and yang is important in various Asian religions and philosophies. The concept is that the world is full of various dualities, such as dark and light, or male and female. These dualities are interdependent, and in their interaction they create new things. These are all manifestations of the yin and the yang. This symbol has been recreated in many ways in LEGO form:
My all time favorite has to be this by Noddy.
To fully appreciate this MOC, you have to also look at it from above.
Lego27bricks recently did something similar.
Here's my own effort.
The yin/yang symbol provides a backdrop to martial artists by pguenthe ...
... and Collin Ballantyne.
Heath Flor celebrated Talk Like a Pirate Day a couple of years back with ninjas vs pirates.
The opposition is shown here by Madformax1.
Here's Remyth's Temple of Yin and Yang.
Jim Walshe ...
... and ANVRecife have had some fun with photography.