In mathematics, a function can map elements from one set (domain) to another set (codomain). A subset of the domain can be mapped to a subset of the codomain under this function. The relationship between the subsets and the function can be visualized by showing how elements of the subset from the domain relate to the elements in the codomain.

To generate an image that represents subsets under a function, I can create a diagram with the following elements:

1. A domain (represented as a circle or oval containing elements).
2. A codomain (another circle or oval).
3. A function mapping elements from the domain to the codomain (arrows connecting elements).
4. Highlighting of specific subsets in the domain and their corresponding subsets in the codomain.

Let me know if you'd like to specify any details for this illustration or if you'd like me to generate it right away!