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Laughing Kids Learn: DIY tugging box for young toddlers
How to Create an Upcycled Inventor's Box for Hours of Open-Ended Play
Upcycled Inventor's box - awesome activity for teaching kids about recycling and creativity. Be sure to get the free printable idea cards!
Tinker Box for Inspiring Little Inventors
Best toys for building STEM (science, technology, engineering & math) skills - love the range of ages covered here.
Gum drop engineering to build STEM skills - post has great tips on extending the activity too