Did you know you can build an amplifier for your cell phone using LEGO DUPLO bricks? This is a fun STEM experiment for children, where they can start to learn about sound waves. Create a box out of LEGO DUPLO bricks, turn on some music and let your pre-schooler hear how the sound gets louder when you put the phone in the box. Make different shaped speakers and try to see which shape makes the loudest sound. Then, of course, make sure you have a dance party!