This book explores and discusses the different perspectives stemming from the visa as a tool of international mobility. A visa has a multiform nature. It is a `key’ which allows aliens to reach the door of the State. It is also a tool for the State to govern migration and border control. In humanitarian and international protection terms, it is also a tool for human rights protection. Against this background, this book assesses the legal and socio-political implications arising from the multipurpose nature and scope of visas. It is divided in two parts. The first focuses on the visa as an instrument for migration control, contextualizing the rationale behind its invention and the legal challenges it raises. The second part focuses on the visa as a tool for asylum, examining its use for humanitarian purposes, including resettlement schemes and emergency-related evacuation initiatives put in place in different legal systems. It will be of interest to academics, researchers and policy-makers working in the areas of Migration and Asylum Law, International Human Rights Law and Political Science.