Fast Company spoke to Bob Messerschmidt, who worked on the heart rate sensor for the Apple Watch after his startup was acquired by Apple in 2010, about the lessons he learned during his time at Apple. Some of the most interesting bits were Messerschmidt’s description of how designers and engineers interact on a product like the Apple Watch:

One great example is [when] I went to a meeting and said I’m going to put sensors in the watch but I’m going to put them down here (he points to the underside of the Apple Watch band he’s wearing) because I can get a more accurate reading on the bottom of the wrist than I can get on the top of the wrist. They (the Industrial Design group) said very quickly that “that’s not the design trend; that’s not the fashion trend. We want to have interchangeable bands so we don’t want to have any sensors in the band.”

Like many before him, Messerschmidt was also impressed by Apple’s focus on products over technology:

At Apple I learned that design and user experience is everything when it comes to consumer products. It’s not so much the technology. It’s the design of the product that creates that sense of happiness in the user.

If you look at products like the iPhone or the iPad there aren’t too many totally new technologies included in those products. The real elegance and differentiation doesn’t have a lot to do with the technology idea itself; it’s about the packaging and the value add it gives to people. Those big (new technology) ideas generally happen elsewhere, and they happen earlier.

Messerschmidt’s interview is particularly notable because it’s not often we get a perspective on the interplay between Jony Ive’s design team and Apple’s engineers.