This E-Lecture introduces virtual seismology: monitoring the subsurface with virtual sources and receivers, which is a new methodology to create virtual sources and virtual receivers in the subsurface from reflection measurements at the earth’s surface. Unlike in seismic interferometry, no physical instrument (receiver or source) is needed at the position of the virtual source or receiver. Moreover, no detailed knowledge of the subsurface parameters and structures is required: a smooth velocity model suffices. Yet, the responses to the virtual sources, observed by the virtual receivers, fully account for multiple scattering. This method is not only useful for reflection imaging but is has also large potential for monitoring induced seismicity, characterizing the source properties and forecasting the response to potential future induced earthquakes. This will be demonstrated with numerical models and preliminary real-data results.​