Anong magandang edad payagan ang anak mo gumamit ng gadgets?

A lot of people are saying that gadgets are not good for children. But l have a nephew who is now 3yo. And he's well versed about gadgets. He doesn't personally have his own. He was just borrowing his mom's gadget. At first he was just observing on how to use it. Then nakaunang hawak na siya until naging magaling na talaga siyang humawak nang gadget. From cellphones, to tablets to an ipad. He knows it all at age 3. My point is, nobody taught him on how to use all these gadgets. He learned it on his own by just learning one particular gadget. Minememorize niya lang visually ang lahat nang icons even the back button and next button sa ibang gadgets. He knows where to find it. He's even a pro than my mom. What l'm saying is he was able to think, develop his skills visually, coordination of his hands at an early age, to solve his confusion, etc...l mean there are advantages and disadvantages in using these gadgets. All they need is to keep our eyes on them and guide them first in our homes on how to use it right. Because out there people have hundreds of them and might teach them the wrong way.