The concept of personhood becomes increasingly controversial in modern legal debates. The advancements in the contemporary science and technology entail the need for reconsideration of who should count as a person in law and why. Animals, cyborgs, artificial agents and the like may pose the most important challenge for the legal orders in the 21st century. The volume collects essays addressing various aspects of this challenge and provide an overview of what may become the most interesting and far-reaching dilemma for the law in the years to come.