Giuliana Rancic paid a touching tribute to her good friend, mentor and 'Fashion Police' co-host Joan Rivers.

The 81-year-old funny woman worked with Rancic on the show for the past 13 years and in an official statement, Rancic verbalized her fondness for the "true genius," according to US Weekly.

"It is almost impossible to describe how much I adored Joan and how much she has meant to me. She was not only the funniest woman I have ever met but was incredibly loving, honest, and lived her life with no regrets. Working with her for the past 13 years has been one of the true joys of my life. She could put a smile on your face, instantly, no matter how hard your day was."

Rancic also sent out her condolences to the Melissa, Rivers' daughter whom she left behind, E! News reported.

"My heart goes out to Melissa and Cooper who have lost something that can never be replaced. Their bond was truly one-of-a-kind. They had the greatest mother and grandmother anyone could ever hope for."

"My life is so much fuller and happier because I got to share it with this beautiful person, a true genius. I woke up today unable to grasp what the world will be like without her and at the same time feel so privileged to have called her my friend," Rancic concluded.

Meanwhile, fellow "Fashion Police" co-hosts, Kelly Osbourne and George Kotsiopoulos also expressed their mourning via social media.

Osbourne took her thoughts to Facebook and revealed how extremely heartbroken she is over the death of the comedian. She also called Rivers "the Grandmother" she ever knew.

"I'm completely heartbroken by the loss of my beloved Joan. Not only was she my boss, she was and will always be my teacher, therapist, closest friend, inspiration and the only grandmother I never knew," Osbourne wrote.  

Kotsiopoulos on the other hand tweeted, "Rest in Peace @Joan_Rivers. Thank you for changing my life. I will miss you so much."