When using balance many different types of artist can focus on different types of balance here is an example of assymetrical balance.
Dominant forms
Most compositions have have multiple parts. A primary form is usually held in balance by one or more subordinate forms like the spheres in this image.
Proportion
Size is relative so when there are multiple parts to the image they are relative in proportion. Notice the differences in their proportions and how they react to one another in the composition.