Let the countdown begin! Marvel fans are just one full day away from experiencing Marvel's Agents of S.H.I.E.L.D., debuting Tuesday, September 24 at 8 PM ET with the "Pilot" episode. ABC is getting fans ready for this highly-anticipated event, with a trailer that aired earlier tonight during ESPN's Monday Night Football pre-show, Monday Night Countdown. Take a look at the latest footage from this highly-anticipated series created by Marvel's The Avengers director Joss Whedon, Jed Whedon and Maurissa Tancharoen.