Jennifer Aniston's hair has been a topic of conversation since her first appearance on Friends. So much so, in fact, that her character Rachel's signature tresses inspired a haircut trend of the same name. Now, we know one of her real-life secret weapons: Olaplex No. 3 Hair Perfector Repairing Treatment. The Morning Show actress revealed to Marie Claire that she uses the treatment 'once a week,' dubbing it one of her holy grail hair finds. "I use an Olaplex hair mask once a week and I often let my hair air-dry to avoid damage caused by hot styling tools," she said.