Despite celebrating her 55th birthday last week, Desperate Housewives star Teri Hatcher looks better than ever and credits a newfound fitness philosophy to finally feeling "comfortable" in her own skin.

Hatcher - who is also well known for playing Lois Lane in the hit nineties show Lois & Clark: The New Adventures of Superman - candidly opened up about her "55-year-old body" in a candid Instagram post that she shared with her 370,000 followers.

Hatcher has recently completed an eight-week workout challenge with F45 Training, which describes themselves as "innovative, high-intensity group workouts that are fast, fun & results-driven."

Check out Hatcher celebrating the end of her workouts on her 55th birthday:

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The actress flexed and showed off the results of the training program while donning a stunning brown bikini. Hatcher captioned the post:

"Exercise has become a source of well being not a means to look good naked. As part of my @f45_training 8 week challenge we had to submit an after photo.

"So why actually post a pic of myself in a bikini? Well, this is my truth and being in this 55 year old body actually feels liberating. Here’s the thing. I’ve finally figured out how to be comfortable in my own skin. Maybe not every day but a lot of them.

"Age allows you to be clear on your purpose and cherish who and what you are grateful for. You have enough age to see the miracle of life and enough youth to revel in that knowledge. You can be vulnerable and strong at the same time. You can forgive others and yourself. You are willing to put in the effort to reach a goal...or not. And that’s okay. Mostly, you know to make the most of every moment. For me that is sharing joy & positivity, knowledge I’ve gained through experience both successes and failures, and helping to lift others up.

"Sharing myself in a bikini (which I may or may not ever wear again) Is me Being open to others, open to life... finding glorious connection and community. No filters, no makeup, no airbrushing, no negativity.

"Be strong enough to be vulnerable. [sic]"

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Back in 2018, Hatcher and daughter Emerson Tenney ran the New York City Marathon in order to raise money for Save The Children. Prior to the race, Hatcher told People Magazine that it was the first time she was running a marathon with somebody else, having ran her first five by herself:

"We have a really close great relationship, but I think that she would say, and I agree with this, that this is different than just going on a trip or spending time together."

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Hatcher continued:

"Something about the ups and downs of training for such a physical feat as a marathon - that sort of vulnerability, the adversity that you have to get through and pushing through walls together - and having that experience as a team; it’s just a bonding thing that you can’t really replace or have from any other experience. And I think we both wanted that together."

Hatcher really is an inspiration that age is just a number!

Teri Hatcher, 55, shows off incredible bikini body as she opens up about fitness