He also became a US citizen during this time. He then completed his residency in neurosurgery at the University of California, San Francisco, where he also completed a postdoctoral fellowship in developmental and stem cell biology at the laboratory of Professor Arturo Alvarez-Buylla. Quiñones began his career at Johns Hopkins School of Medicine, where he became a Professor of Neurosurgery and Oncology, Neurology, and Cellular and Molecular Medicine and director of the Brain Tumor Stem Cell Biology Lab. His clinical interests focus on the surgical treatment of primary and metastatic brain tumors, with an emphasis on motor and speech mapping during surgery. He is expert in treating intradural spinal tumors as well as brainstem and eloquent brain tumors in adults with the use of neurophysiological monitoring during surgery. He further specializes in the treatment of patients with pituitary tumors using a transphenoidal endonasal approach with surgical navigation and/or endoscopic techniques. He has a strong interest in treating patients with skull base tumors and the use of radiosurgery as an adjunct to the treatment of these lesions. Quiñones conducts both clinical and basic science research. From 2005-2016, his team published over 150 scientific articles and received 14 funding grants. Quiñones conducts numerous research efforts on elucidating the role of stem cells in the origin of brain tumors and the potential role stem cells can play in fighting brain cancer and regaining neurological function. He has been actively involved in fund raisers for brain cancer research. He continues to participate at half-marathons with his research team and some of his own patients to raise money for cancer research. In April 2016, Quiñones was hired by Mayo Clinic in Florida as its William J. and Charles H. Mayo Professor and chairman of Neurosurgery. He left Johns Hopkins and started work at Mayo Clinic Florida in Jacksonville. His clinical work includes: In addition to his clinical activities, Quinones-Hinojosa leads NIH-funded research to find a cure for brain cancer. His research focuses on brain tumors and cell migration, healthcare disparities for minorities and clinical outcomes for neurosurgical patients. He is also researching new techniques in neurosurgery such as the use of nanotechnology and focal beam radiotherapy, the development of new imaging software to identify areas of tumors, and the development of innovative, minimally invasive approaches to brain tumor resection in the systemic treatment of solid tumors. Quiñones is the author of more than 50 book chapters and has authored several textbooks on neurosurgical techniques and stem cell biology.