Tamim Alnuweiri / InStyle: Martha Stewart, 84, Spent 5 Years Developing Her Own Skin Care Brand-Including the Serum That Improves Her Skin's "Texture and Tightness" - It's the first launch from her new skin care brand. ... Martha Stewart is 84 years old and has some of the most enviable, smooth, radiant, and seemingly pore-free skin.