Dr. Caitlin Snow is a bioengineering expert and a crucial part of Barry Allen's S.T.A.R. Labs support team.

During that fateful explosion at S.T.A.R. Labs she lost her fiancé, Ronnie Raymond. At least that is what she believes when she meets Barry Allen. The character is described as the ice to Ronnie's fire, foreshadowing their future metahuman abilities from the comics.

Dr. Caitlin Snow/Killer Frost Quotes

Caitlin: Ronnie's alive. I saw him Cisco. I think he was following me...
Cisco: Caitlin, Ronnie died. He was vaporized in the accelerator when it went critical.
Caitlin: Ronnie's alive and he's out there, alone and scared and I need your help to find him.

Caitlin: Since when do we have facial recognition software?
Felicity: Happy Hanakuah.

The Flash Quotes

Captain Cold: Make the plan. Execute the plan.
[King Shark appears]
Barry: Expect the plan to go off the rails.

Barry: From Oliver and Felicity, we have an...expresso machine!
Iris: Okay, not on the registry, but I guess getting married during our wedding wasn’t on the registry either. So, yeah, sure.
Barry: Alright...
Iris: I'm not bitter.