What age is best to start a STEM electronics kit?

Most reviewers across the kits we read agree that 5-7 year olds do best with simplified, large-component sets like the Snap Circuits Beginner (SCB-20), where parts snap visibly together and projects are short. The 8+ kits like Snap Circuits Classic SC-300 and Klutz Lego Gear Bots assume the child can follow a multi-step diagram. Specialist-subreddit consensus is that an adult should plan to co-build with younger kids regardless of stated age.