The physical aspect of transforming Steve Rogers into Captain America is one of the movie's stellar effects. In fact, the effect involved creating a skinny Steve from the buff Captain America body that actor Chris Evans attained from months in the gym.
In World War II patriotic solider Steve Rogers recipient of the "Super Soldier Serum" became the living symbol of freedom, Captain America. Left for dead while frozen in ice, the star-spangled hero with an indestructible shield awoke years later to continue his never-ending battle for liberty.
In the aftermath of Civil War, Captain America is taken into S.H.I.E.L.D. custody where he is assassinated per the order of the Red Skull. Crossbones snipes at him while Sharon Carter (Agent 13; Cap's girlfriend), who has been brainwashed by Doctor Faustus, posing as a S.H.I.E.L.D.