Beatriz Gato Rivera, also known as B. Gato, is a Staff Scientist at the ‘Instituto de Física Fundamental’ (IFF, Madrid, Spain) of the CSIC (Spanish National Research Council). After finishing her Ph.D. on the topic of Supergravity, she spent three years at the Massachusetts Institute of Technology (MIT, Cambridge, USA) and another three years at CERN (Switzerland), working on String Theory. She has been the Principal Investigator of four research projects. In addition, at the IFF she was the head of the department of ‘Particle Physics and Cosmology’ for four years, and coordinator of the ‘Mathematical Physics’ group from 2008 until 2019. Her scientific interests are centered on Mathematical Physics, Particle Physics, Gravitation, and Foundations of Quantum Mechanics. In the last ten years she has also been involved in outreach activities, especially public talks, and in 2018 she published the book Antimateria in CSIC's collection ‘¿Que sabemos de?’. This was thebasis for the much extended and updated English version now available as the present volume “Antimatter”.