At what age did you let your baby watch TV/iPad?

My Tita said that she did not expose her baby to gadgets like TV/tablet of even smartphones up to age 4. I know that nowadays, kids as early as 2 years of age are exposed to these kinds of gadgets. My Tita said that she personally did not let her kid be exposed to these for the following reasons: 1. health risks--too much radiation, bad for the eyes, etc. 2. she wants her kid to be physically active and enjoy playing actual games than be entertained by different apps.