It’s a balancing act. If you try to force it, it becomes un-fun. Don’t let STEM become the thing that your children dread because it was always pushed upon them.<p>Figure out what children enjoy and provide opportunities around that. Things like LEGO are a good introduction, if they’re into LEGO. Programming-style games are fun, if they’re into games.<p>Doing things with your child can make them interesting (up until the age where you become uncool, of course).
Background and caveat. I am that uncle the parents fear. I let my nieces and nephews do about anything they want - until the wife-unit shuts it down...<p>1. Note any disposition for science or engineering - it was obvious very early (pre-school) in a particular niece and nephew. One other did not develop said disposition until well into high school.<p>2. Provide an environment. A nephew used to play with my o-scope and function generator during his early grammar school years and played with other stuff on my bench. He later watched me model stuff using MathCad in the 90s. And he recently got (yet) another degree in computational physics.<p>3. Be logical. Allow curiosity. Allow and never disparage supposedly 'self-evident' questions.<p>4. When a STEM interest is noted, be ready for the "what is the difference between science and engineering?" question. Do not mistake a STEM interest for a desire to pursue a STEM career. The others nieces and nephews are, or will become, ranchers, business people, and artists; and the artists were probably the most intelligent of the lot.<p>5. Exposure to, and enjoyment of, an activity are not the same thing and will not necessarily result in similar outcomes.
Have a conversation with them about something, "wanna know something cool about rocks/insects/stars/the ocean/numbers/... ?" -- share things that you found exciting and interesting with them. :) From there you can do research projects together, watch documentaries, buy them equipment to allow them to engage their interests (microscopes and telescopes come to mind).