Rubén S. Montero, PhD is an associate professor in the Department of Computer Architecture and Systems Engineering at Complutense University of Madrid. He is also co-founder and Chief Technology Advisor at C12G Labs. In the past, he has held several visiting positions at ICASE (NASA Langley Research Center, VA). Over the last years, he has published more than 80 scientific papers in the field of High-Performance Parallel and Distributed Computing, and contributed to more than 20 research and development programmes. His research interests lie mainly in resource provisioning models for distributed systems, in particular: Grid resource management and scheduling, distributed management of virtual machines and cloud computing, where he is especially interested in the inter-operation of cloud infrastructures. He is also actively involved in several open source grid initiatives like the Globus Toolkit and the GridWay metascheduler. Currently, he is co-leading the research and development activities of OpenNebula, a distributed virtual machine manager.