A3 COSMOS is a joint project between our research group and that led by E. Schinnerer at the Max-Planck-Institut für Astronomie (MPIA). Its goal is the full exploration of the ALMA observations toward millions of galaxies in the COSMOS two square degree field. ALMA is the most powerful and sensitive (sub)mm interferometer array, but its small field of view (~30") makes dedicated large-area surveys too expensive to be pursued while being needed to better understand galaxy formation. Fortunately, through many individual Principal Investigators observations, ALMA has deeply mapped an increasing area in some of the most popular extra-galactic fields, like COSMOS. Our project goal is to exploit this growing ALMA science archive to “create” a deep (sub-)millimeter survey covering an ever-increasing fraction of the COSMOS field. This homogeneously reduced database is provided to the COSMOS collaboration and the whole astronomical community, and can be used to best understand formation of galaxies by measuring, for example, their star formation and interstellar medium properties or performing blind CO and C + line searches. Based on these ideas, we developed within the German ARC node an automatic tool to query, retrieve and image the ALMA archive. The MPIA group performs the source extraction within these images and cross-match those with the wealth of panchromatic observations available in the COSMOS field. With this process, which we repeat every 6 months, our database currently cover ~340 square arcmin area and 5% of total galaxies detected in the COSMOS field. This effort allows ourr research groups to pursue already a whole new set of scientific studies.