My research career began when in 1981 I joined the Molecular Biology Center in Madrid to start my doctoral thesis on the synthesis of photoactivatable streptomycin derivatives, which were used to determine the antibiotic ribosomal binding site. After the defense in 1985, I obtained a position as Assistant Professor at the UAM, thus beginning my university teaching. In 1987, under the direction of Professor Charles Cantor of the Columbia University in New York, I participated in the development of methods for the construction of physical maps of human chromosomes, at the beginning of the human genome project. When I returned, I rejoined my assistant position and together with Dr. Amils co-directed two doctoral theses for the construction of physical maps of microorganisms in a pioneering work in the application in our country of pulsed field electrophoresis (PFGE). In this period, together with Dr. Alfredo Villasante from CSIC, we started a project to study the structure of eukaryotic chromosomes, using the Drosophila melanogaster model. Genomic libraries were constructed in yeast artificial chromosomes, cutting-edge technology at that time, which allowed us to discover a centromeric Drosophila satellite that served as an entry point for the study of that chromosomal region. We also studied the structure of telomeres, discovering a transposon that participates in its maintenance. These works were reflected in the co-direction of a doctoral thesis together with Dr. Villasante. An important milestone in this path was the elucidation of the disposition of the telomeric transposons in 12 species of Drosophila and that was published in Nature as part of a collaborative work of numerous researchers. Another important milestone of this stage was the discovery that centromeric and telomeric sequences could have a common evolutionary origin. In 2008 I was granted a research lab to start a new line of research on a subject that, in some way, returned me to my origins since it was to study the resistance to antibiotics in the environment as a possible source of many of the resistances found in clinical environments. Unfortunately, the economic crisis that began in those years and the change in the line of work made the development of research difficult, preventing to obtain the necessary financing. This difficulty could be partially avoided by resorting to collaborative projects with third-world groups sponsored by the AECID. These projects allowed me to continuously maintain my research activity, although certainly limited by the precariousness of the available resources. The AECID also granted a scholarship to carry out the doctoral thesis to a student of African origin, which had to be carried out in a period of only three years and which was defended in January 2016. Another doctoral thesis was co-directed by me together with researchers from the Institute of Advanced Studies in Nanotechnology of Madrid in this period. In it, silver nanoparticles were obtained by biological methods and characterized, publishing a relevant article in this field. I have been working since in this line of research, which has produced up to now two end of grade projects and one Master thesis, which results are in process of publication.