Lumos was my first attempt at building a "company." It's an automated eye disease screening kit, composed of a ~$30 lens you can clip onto the back of a smartphone to capture photos of the retina (vs $1000+ slit lamps / ophthalmoscopes), and a set of computer vision algos that screen for various eye anomalies like glaucoma, macular degeneration, etc.
I built the first working prototype my senior year of high school as my science fair project, then got serious about building a company around it freshman year of college. I recruited a cofounder, built serious personal relationships with a few doctors / advisors, got IRB approval at 3 hospitals and was on track to go through clinical trials and start FDA approval process, and got a YC interview at 18 y/o.
The problem was Lumos started as a science fair problem, thus was fundamentally a technology looking for a problem to solve -- we had no idea who our customer was, and we had no grand vision of what we wanted the world to look like in the future, and how Lumos would make that happen.
Ultimately, after some harsh learnings, we looked around and realized we didn't really understand what it took to build a real company, and decided to go finish school. This experience is what ignited a deep desire to pursue building an exceptional company, even though I'd still have many failures along the way. Through Lumos I also uncovered a deeper understanding of the mess of problems in healthcare, and discovered a great passion for trying to solve them in the future.