To complete the demonstration of personalized law in action, this chapter focuses on the inputs used to tailor the individualized commands. One input that is likely to feature in the personalization of many rules is age. Age is informative because it is often correlated with personal attributes that matter to achieving the goals of a law. Preferences, cognition, judgment, experience, and physical ability—all vary with age. Young age is a factor in the denial of legal capacity and in the conferral of various paternalistic protections, whereas old age represents changing needs, capacities, and entitlements. Under personalized law, age would be an input affecting legal commands that are currently age-invariant, such as the intestate succession default rule or speed limit laws. In addition, age of capacity laws, which are currently used to regulate entry into various activities, would use different age cutoffs for different people.