What Are The Most Important Unanswered Questions In Science That Are Likely To Be Answered By 2025?

What are the most important unanswered questions in natural science that are likely to be answered by 2025? What are the most important unanswered questions in natural science that are likely to be answered by 2025? It's difficult to say, partly as it's hard to know which questions are within our reach and partly because it's impossible to say which questions are the "most important". I personally think the greatest unanswered questions lie within the human brain. Specifically, we still have little understanding of the connection between the different levels of brain hierarchy: from detailed molecular mechanisms to the understanding of whole neuron cells, to entire neural networks comprising billions of cells and inter-neuronal connections.