Will the most extraordinary scientific discoveries be made in biology?
This is obviously a very subjective matter. Let me put forth why I think the most dramatic discoveries will be made in biology.
In the early 20th century, the most dramatic advances were in physics. Relativity and quantum mechanics resulted in a revolutionary change in how we view the universe. We still don’t have a theory of everything to unite the two fields, but we are quite capable of cobbling together the two theories to make rather accurate predictions. I may be wrong, but I don’t see further developments having the same impact as the initial ones.
The latter part of the 20th century saw the discovery of the structure of DNA. This was rather remarkable, but I see it as just a beginning. There is so much we have yet to learn. Even if we disregard questions on how the brain works, there are still fundamental questions on how even the simplest multicellular organisms grow and maintain their structure. The answer has to involve understanding of individual cells along with knowledge of how they interact. I feel strongly that there are some very non-intuitive discoveries to be made that will cause us to rethink the way the world works.