The European Marine Observation and Data Network (EMODnet) is a network of organisations within Europe that assembles marine data, data products and metadata from diverse sources in a uniform way. EMODnet is supported by the EU’s integrated maritime policy and funded by the European Commission (DG Mare). Presently, there are seven sub-portals in operation that provide access to marine data from the following themes: bathymetry, geology, physics, chemistry, biology, and seabed habitats and human activities. The challenges are tasks that have been chosen to make the bridge with end-user applications and test how comprehensive and accurate the monitoring and forecasting datasets are at the Mediterranean scale. They cover the blue economy sector (offshore industry, fisheries), marine environment understanding (for MFSD health assessments and climate change issues) preservation of natural resources and biodiversity (Protected Marines Areas and red list species), 7 areas altogether: Windfarm siting, Marine Protected areas, Oil Platforms leak, Climate and Coastal protection, Fisheries management, Marine Environment, River inputs. Within EMODnet, it has been recently launched the EMODNET Mediterranean Sea Portal for assessment of observational data systems and targeted applications. The main objectives of this recently launched project (December 2013) are to examine the current data collection, observation and data assembly programs in the Mediterranean sea basin, analyze how they can be optimised, and deliver the findings to stakeholders through an internet portal. Besides this, the portal brings users in connection with the existing observing systems, the assembly and networking and the information&communication technologies systems. Furthermore it links to a Web GIS service containing a collection of GIS outputs.