MOSAIC is the future multi-object spectrograph (MOS) for the E-ELT. After giving a brief overview of the instrument and its operating mode, I will highlight some SFB-relevant aspects of the current phase A study (March 2016 - March 2018), during which the conceptual design of the instrument will be refined. The phase A study includes the preparation of public surveys that could follow the implementation of the instrument at the telescope (~2025-26). Even if MOSAIC is a long-term project, it is now that we have to prepare the design of the MOS and accompanying surveys on the largest telescope of the next decades.