What age will you expose your children to the Internet and social media?

Ideally, I'd want them to wait till they are in the double digits (10 years and above) but obviously that's not happening. I've a cousin who's 6 and she has facebook, instagram, twitter and snapchat. I suppose all we can do as adults is to guide the kids and educate them on both the benefits and dangers of the Internet, social media etc.