This tinker box idea is one of my favorites; there are just so many things I love about it - the open-endedness, the creativity that is inspired, and, in our case, the frugality of it all. Not to mention the fact that Kay just loves it!
I first saw the idea at Left Brain Craft Brain (a bastion of S.T.E.M. ideas, by the way - definitely check it out!). For our version, I converted Kay's old toy toolbox. I left in the place the tools that hadn't yet been lost and added whatever I thought might be useful. The great thing is that there are no rules for putting something like this together - whatever you have lying around will work. (I think the tape is Kay's favorite part though!)
I added pipe cleaners, Scotch tape, bottle caps, toilet paper rolls, craft sticks, glue, glitter glue (for when you need that extra sparkle!), pipe cleaners, scissors, elastics, beads, craft foam, toothpicks, Styrofoam, etc. If you do feel the need to purchase things for your kit, dollar stores are a great place to look (keeping with that frugality thing!)
I think the real secret to our tinker box's success has been that there are almost no rules to go along with it. No, you can't put glitter glue on the dog, but other than that... She can use as much tape or glue as she wants, stick things together that "don't belong". Basically, she's free to try whatever she can think of.
So what can you make with a tinker box? Well, anything, of course! Kay came up with three ideas during one particularly- inspired day. Above, her homemade back-scratcher. And, below, a cardboard tube airplane (complete with craft foam windows) and a decorative medicine cup (much prettier than the plain ones!).
What have your junior engineers come up with on their own?