Some artists spend their whole lives trying to write the perfect song, and for some it comes suddenly. The latter happened with Guns N’ Roses when Slash was just playing guitar and accidentally composed the legendary riff from Sweet Child O’ Mine. It was in 1986:
I was just playing some stupid riff. And Axl suddenly said, “Damn it! It’s brilliant!”
That’s where the song started. Despite the fact that it seemed to the rest of the band members that the riff had no potential, the track was finalized. Time has shown that Axl was right.