Self-care seems to be the name of the game these days, especially with millennials, and it's beginning to manifest itself in fat paychecks for the makers of self-care and digital wellness apps.

According to data from multiple app store intelligence firms, the category of "self-care" - that is, activities or items dedicated to emotional or physical investment in the "self"' - is now seeing notable growth. In the first quarter of 2018, the top 10 grossing self-care apps in the U.S. earned $15 million in combined iOS and Android revenue, and $27 million in worldwide revenue, according to Sensor Tower.

Sensor Tower also discovered that the top 10 wellness apps, particularly pertaining to mindfulness and meditation, made about 170% more revenue worldwide in Q1 2018 than the top 10 wellness apps did in the first quarter in 2017 across both the App Store and Google Play. In the U.S., they made about 167% more. Incidentally, the U.S. is also the place with the most millennial-oriented business endeavors, which is reflected particularly in its notable social media usage and youth-centric movements.

Apple (AAPL  ), dubbed self-care as one of its top four breakout trends for 2017, saying, "Never before have we seen such a surge in apps focused specifically on mental health, mindfulness and stress reduction."

Some notable apps in the category include "Calm" and "Headspace," both of which are focused on meditative practices and capitalize upon the notion of "getting away from it all." In fact, Calm has become a top grosser, earning about half the total revenue in the U.S. and worldwide. This results in roughly $8 million in the U.S. and $13.5 million worldwide. Combined with Headspace, the two generated more than 90% of revenue for the top 10 apps last quarter.

Another big one is "Shine," which just closed $5 million in Series A funding. Shine attempts to transmit positive, uplifting messages on a daily, automated basis to young people who may need a continual reminder of their self-worth.

"Marah and I are both women of color, and we created this company from a very non-traditional background from an entrepreneurship standpoint - we didn't go to business school," says co-founder Naomi Hirabayashi. "We saw there was something missing in the market because wellbeing companies didn't really reach us - they didn't speak to us. We didn't see people that looked like us. We didn't feel like the way they shared content sounded like how we spoke about the different wellbeing issues in our lives," she says.

Some of the self-care craze has very real medical applications. For instance, smartphone apps that monitor pill-taking are now available.

"Selfie medicine" works like this: Open an app on your phone, show your pills, put them in your mouth and swallow. Don't forget to show your empty mouth to the camera to prove today's dose is on its way. Then upload the video proof to the clinic. This helps remedy the problem of antibiotic resistance and treatment that goes awry because medicinal courses aren't completed.

Overall, the market seems to have taken a liking to this new phenomenon, which may be a bright spot in the otherwise troubled tech landscape.