This exploded assembly drawing of the Pro-Form GR 75 exercise machine shows the hidden world of nuts, bolts, washers, and specialized parts within this mostly mechanical product. (Image source: ICON Health & Fitness, Inc.)
STEM starts with bikes. The best reason for giving a child a bike is so they can fix them. Adjust the handlebar, seat, and chain, repair a flat tire, trying to figure out how the brakes work. I think my first bike spent more time upside down than right side up. We learned how to use tools, how to get things back together, and hopefully how to put tools back where we found them.
Later on, going to the neighborhood drug store with a bag of vacuum tubes to repair the family radio or TV was a regular occurance. Unfortunately, this experience is gone forever.
I'm saving a pile of old VCRs and tape players for my grandson to "fix". Hopefully, he'll find it as much fun as I did (do).
I spent lots of hours with my father at his office when I was still a child. He was always repairing and modifying tape recorders, amplifiers, microphones and many other professional audio equipment. I remember how meticulous he was and how he was able to remember every single screw, piece, cable, spring.... everything.
One of the tape recorders from that age I remember with affection is the SONY TC800B, its service manual fascinated me, it had one of the first "exploded" diagramas I had in my hands.
Googling a little I found a PDF of one of this manual's editions, for the TC800, the link is this page here: https://elektrotanya.com/sony_tc-800.pdf/download.html. For grabbing the manual you will have to wait about half a minute, below the preview image there will be a line saying "This file is downloadable free of charge:", the "Get Manual" link will be displayed after some time.