What learning resource has had the greatest impact in elevating your understanding and knowledge of Rust?

Often times when learning a new language, framework, or a subject people will encounter a resource that illuminates the subject matter for them in such a way that it elevates their understanding to a higher plane and forever changes their perspective on the subject matter. Obviously, such an experience is only achievable when it is paired with a healthy amount of practice and learning failures. For me, for instance, The Little Schemer was instrumental in uncovering the beauty of recursion and understanding it deeply. What is an example of such resource for Rust that you have encountered in your learning journey? And what was your main takeaway from it?