STEM toys - toys that encourage learning in Science, Technology, Engineering, Maths - are big business. It's tempting to choose a toy that's all flashing lights and whizzy tech. But is that what the sciences are all about?
But if your goal is to promote exploration and discovery, then the simpler the better. You probably don't even have to buy any toys. Experiment with elastic bands, lolly sticks, corks and water. Count with pebbles and leaves. Make geometric shapes with sticks.
STEM toys for preschoolers need be nothing more than blocks and puzzles, tools and stackers. There's a straight line between block play and counting, maths, engineering and coding, but to your child it's simply more play. Don't worry too much about 'teaching' concepts to your child. Offer the right toys and experiences and allow time for exploration and discovery. Nature will take care of the rest.