This chapter provides a deep dive into a key element of successful commercialization of new devices and delivery systems: understanding the end users. It demonstrates the need to incorporate deep insights of patients and caregivers at various stages, ensuring that both the design and rollout phases address relevant human attitudes and behaviors. This chapter also defines best practices for obtaining those insights appropriately, and sufficiently early in the product development process—describing the role of System 1 and System 2 thinking in the adult decision-making process as it applies to adopting new delivery devices. It also provides some learnings gleaned from case studies in device/administration system development. Finally, it includes some guidelines—the Top Ten Truths—plus resources for validating end user decision-making and adoption.