Ask HN: What are the most interesting fields to apply CS skills to?

People say that there's a lot of value on the intersection between CS and other fields. Like you don't want to just learn programming, webdev, ML, etc, but you want to learn programming + some other field, so that combining them would allow you to solve cool problems, create a lot of value, make profitable startups.

What are some examples of such fields? If you were to apply CS to another field, what are the top 3 fields that would generate the most value? If you were to learn something other than CS (for the purposes of building a profitable startup), what would it be?