The mantra "Identity is the new perimeter" has become a common refrain among security professionals. Yet, many organizations still manage identities as if their workforces had never left the confines of their internal networks. The explosive growth of cloud services, SaaS applications, and a distributed remote workforce has transformed identity management from a catchy slogan into a tangible security imperative. This chapter serves as a practical primer, clarifying what identities truly represent in today's complex digital environment and providing concrete strategies for effectively managing identities at scale. The old approach won't protect us in this new landscape—understanding modern identity security is foundational to any serious security strategy today.