Damon Salvatore's True Love

Sienna Mikaelson, one of the youngest originals amongst them all. She grew up with Elijah, Klaus and Rebekah most of her life.. they all protected her because she was the youngest sibling. Klaus had a soft spot for Sienna. In the 50's Sienna met Damon Salvatore, a very handsome young man. Throughout their years they spent together they formed a "relationship" of the sort.
They went through some shit.. dark shit.
Lot's of stuff goes down between the Mikaelson's and the Salvatore's..
How did Sienna and Damon meet? and what happens when their worlds collide and they meet again?