In this talk, I will compare what MRI can and cannot show in multiple sclerosis at the two ends of the field-strength spectrum: portable ultra-low-field (e.g., 64 millitesla) and ultra-high-field (e.g., 7 tesla). I will discuss how field strength changes image quality and lesion visibility, what you gain (and what you give up) as you go higher or lower, and how to choose the right approach for the clinical question. I will highlight examples where 7T can add biological insight (e.g., susceptibility-based lesion features, such as how lesions develop around veins in both white matter and gray matter) and where low-field systems can expand access and enable point-of-care imaging. Level of Information: Basic, IntermediateIn this talk, I will compare what MRI can and cannot show in multiple sclerosis at the two ends of the field-strength spectrum: portable ultra-low-field (e.g., 64 millitesla) and ultra-high-field (e.g., 7 tesla). I will discuss how field strength changes image quality and lesion visibility, what you gain (and what you give up) as you go higher or lower, and how to choose the right approach for the clinical question. I will highlight examples where 7T can add biological insight (e.g., susceptibility-based lesion features, such as how lesions develop around veins in both white matter and gray matter) and where low-field systems can expand access and enable point-of-care imaging. Level of Information: Basic, Intermediate