This chapter compares and describes the biometrics and physical object security fields, based on physical unclonable functions. Both lay at the foundation of authentication and identification architectures based on the assumption that the used primitives are both nonclonable and unique. First, it will cover the physical phenomena that form the basis for both biometrics and physical object security next to highlighting the specificities of the used verification schemes. Second, it will cover relevant properties and requirements such as the security principles, feature extraction, the effect of leaks, possible attack vectors and the practical technological requirements needed for the implementation.