Our story
Built by people who actually care how their skin ages.
The90 exists because the most consequential variable for how your skin ages (daily UV) has never had a meter. Until now.
Founding story
I didn’t set out to build a wearable. I set out to answer a question my routine couldn’t: why was my skin changing when I was doing everything “right”? The serums, the SPF, the diligent reapplying — and still, new spots, new lines, always after the seasons I remembered most fondly.
The deeper I went into the research, the clearer the gap became. UVA — the aging ray — passes through clouds and car windows, and almost nothing in a consumer’s toolkit measures it. The medical literature had known for decades. The tools simply didn’t exist.
So instead of writing about the problem, we decided to build the meter. A sensor precise enough for the science, and beautiful enough that you’d actually wear it every day.
The future of skincare isn’t more products. It’s measurement. That conviction is The90.
We believe the next decade of skin health belongs to people who measure. The90 builds the tools that make that possible. Starting with the rays that cause 90% of visible aging.
Team.
Stacy
Co-Founder & CEO
Dr. Weller
Professor & Dermatologist
Backed by people we’d trust with our own skin.
If you care about how skin ages, how light works, how wearables are built, or how brands grow. We want to hear from you.
Is there a subscription or monthly fee?
No. Your Gem comes with the full The90 app and every core feature, with no monthly fee to read your own light. You buy the sensor once.
What does The Gem actually measure?
It reads the UVA and UVB reaching your skin, separately and in real time, then turns the day into a single Sun Score from 0 to 100. Along the way it tracks the light you want, like your morning circadian light and your estimated vitamin D, and the exposure you want to manage, like the UVA that ages your skin.
Do I have to wear it as a necklace?
It comes as a jewelry-grade pendant on a matching gold or silver chain, so you can wear it out of the box. The Gem is also a removable core, so it can move into new ways to wear it as they launch, including a hat clip and bag tag on the way.
How is this different from the UV Index or my weather app?
The UV Index gives one number for a whole city and says the same thing to everyone. The Gem measures the light actually hitting your skin, separates the aging rays from the higher-energy ones, and reads it against your personal skin profile in real time. It is the difference between a forecast and your actual day
Can I wear it in the water?
Rain, sweat, and a quick rinse are all fine. The Gem is water resistant to 1 meter for 30 minutes, so leave it off for the pool, the shower, hot tubs, and saunas.
What if it is not for me?
Try it for 30 days. If it is not right, send it back for a full refund, and every Gem is covered by a 1-year warranty. Free shipping, dispatched from California within 1 to 2 business days, currently within the US.
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