The applications of MIGA extend from monitoring the evolution of the Earth gravitational field to providing a new tool for detecting gravitational waves. By combining geophysics and fundamental physics application in a single infrastructure, MIGA will lead to an unprecedented step in understanding geophysical phenomena and will allow for extending the low frequency sensitivity of future gravitational wave detectors. It will keep France among the leaders in many major fields; fundamental physics, matter wave interferometry, geophysics and gravitational wave astronomy.