Additional Study Information: The Snapshot study aims to understand brain and spinal cord aging in healthy individuals and individuals with multiple sclerosis (MS). We aim to identify new tools that will help us to achieve successful brain aging in the general population and in people with an underlying autoimmune disease. A critical aspect of this study is that we are looking for individuals who are willing to donate their brain and spinal cord when they pass away; this will enable the investigators to understand which molecules in the brain made someone more or less likely to age successfully. The brains will be housed at the New York Brain Bank. The study is primarily online, with cognitive evaluations every three years. A subset of participants will be invited for in-person visits, blood sampling, and more detailed examinations of brain function. By collecting data during participants' lives and later on collecting brain tissue gives us a rare opportunity to understand how to improve the way we age to maximize function.