COSI is a wide field of view gamma-ray telescope that obtains high spectral resolution from 0.2 to 5 MeV, enabling sensitive narrow line imaging of the entire Galaxy. COSI’s sensitivity coupled with its daily, full sky coverage will both revolutionize our understanding of creation and destruction of matter in our Galaxy and beyond and open this window for further exciting new discoveries. COSI will resolve the glow of antimatter annihilation in the Galactic center. COSI’s map will substantially deepen our understanding of the positron life cycle, including where and how positrons are produced. The gamma-rays from elements formed in supernovae and other stellar processes penetrate the surrounding material, allowing COSI to reveal the sites of element formation. COSI will map radioactive Al26 with unprecedented sensitivity and angular resolution and will make the first map of Fe60. COSI’s Ti44 map will uncover young, hidden supernova remnants. COSI will illuminate the extreme environments of gamma-ray bursts and accreting black holes with pioneering MeV polarization measurements. COSI is a key contributor to the burgeoning field of multimessenger astrophysics. With its wide field of view, energy range, and localization capabilities, COSI will perform powerful searches for electromagnetic counterparts to gravitational waves and high-energy neutrinos.