Collects S.H.I.E.L.D. #1-6. Leonardo Da Vinci was an agent of S.H.I.E.L.D. So was Issac Newton. And many other geniuses throughout time. They were the first heroes to defeat Galactus and the Brood and turn Celestials back. They saved the world long before Captain America or Iron Man were ever born, but what does this mean to our heroes of today?