From basic building blocks to DUPLO blocks to LEGO blocks, your kids have always loved toys for building. If you have budding engineers or architects on your hands, you ought to look into K'NEX toys. A K'NEX set can help your kids learn about spatial relations, math and geometry, and physical science. With the proper toys, children can learn all on their own about simple machines and physical principles, and of course, exercise their creativity and fine-tune their eye-hand coordination. If you are just getting started with K'NEX, buy a set that comes with directions. As the kids get comfortable with the K'NEX building process, they can branch out and invent their own buildings and machines. When they get to this point, search on eBay for a K'NEX lot. In one purchase, you can get a huge variety of pieces, and the kids can exercise their ingenuity as they put the pieces together in various ways. New toys can be expensive, but search through the inventory on eBay for gently used K'NEX as well as new pieces. Take advantage of convenient shipping options, and your future engineers can be playing in no time at all.