Italian Gambit

The Italian Gambit is a chess opening that begins with the moves:
It is often played as an alternative to the quiet and closed lines of the Giuoco Piano or Giuoco Pianissimo openings. Black can:

take with the pawn, a transposition to the Scotch Gambit;
take with the knight, which is considered weak since it allows 5.Nxe5, attacking f7 with the bishop and knight; or
take with the bishop, which is considered best.

4...Bxd4

After 4...Bxd4 5.Nxd4 Nxd4:

6.0-0, favoured by George Koltanowski, transposes to the related gambit line 4.0-0 Nf6 5.d4 following 6...Nf6, when 7.f4 and 7.Bg5 are the main possibilities for White; however, 6...d6 is an independent alternative for Black.
6.Be3, dubbed the Miami Variation by Jude Acers and George Laven, is a way for White to deviate that probably suffices for dynamic.
6.f4 is considered dubious due to 6...d6.