A an eyelash or eyebrow or fell into my eye one time and irritated me for days to weeks. I didn't realize why of course, but when I finally realized, the hair had grown over an inch. I recognized it was an eyelash hair or eyebrow hair because the first centimeter of it or so was hard, but the other 1.5 centimeters was much much softer. Apparently, between the eyelid and eye is a ideal place for some hairs to continue their lifespan :) This led me to realizations though...
From my eyelash-in-wrong-place experience, I learned cultivating bio growth was not very hard. I'm not certian, but I'm pretty sure I've seen this type of thing in the insect world as well. I wonder- exactly how well can this process be manipulated? If I had the time, money and space, I'd love to conduct some experiments. I think it is not only possible, but likely that an entire livable structure could be formed from a hard insect shell.
Cars could be made, houses, shoes- whatever we need and it would be more "eco-friendly" or "green." Personally, I'd like to see some balance in this world of metal. I know it seems really far fetched and while I'm stretching... It's also possible to produce muscles in place of gears. So how would you get those muscles to do what you need them to? Pressure-points for tension control, or electric stimulation for a little blend of metal and flesh.