Nicolás is Researcher at the Centre for Constitutional Studies of the Supreme Court of Mexico; Guest Lecturer in Law and Member of the Editorial Board of the Leiden Children's Rights Observatory (University of Leiden); Corresponding Member of the Cambridge Family Law Centre (University of Cambridge) and the Nordic Centre for Comparative and International Family Law (University of Aalborg); Visiting Fellow (2019-2021) at Exeter College (University of Oxford ) and Chair of the International Network on Constitutional Family Law (INCFL). Nicolás has been a permanent advisor to the United Nations in the field of children's rights and has extensively researched and published on children's rights, comparative constitutional law, family law and access to justice for children and adolescents, migration, disability and law, social rights, and legal theory.