This paper provides my current perspective on these two challenging issues, and how they both depend on our ability to accurately estimate rate coefficients and related quantities. In this paper I particularly focus on recent attempts to use machine-learning methods to provide the numerical estimates, which potentially could change how estimation is done. A large number of very talented researchers are currently working on these problems, and many more have worked on them in the past. There are volumes devoted to parts of this problem and many reviews of different aspects of the problem. . Here I do not attempt a comprehensive review of this big research area, but instead focus on some specific aspects of these big problems that I am most familiar with, mostly due to recent work done by my collaborators.