How early can kids learn coding?

My son started when he was 5 with a coding puzzle app called Lightbot Jr. If you're interested in getting your child started on digital literacy, Google x Saturday Kids x 21C Girls is running a free full day coding camp at Google's offices this Saturday (boys can join too!). https://www.eventbrite.sg/e/google-x-saturday-kids-x-21c-coding-camp-aug-27-2016-tickets-27256620285