The World Health Organization has issued its first guideline for kids' exposure to electronic screens, including smartphones.
The guideline says children younger than a year old should not be exposed to ANY electronic screens, while those aged two to four should have no more than one hour of "screen time" a day.
Such activities include playing computer games and with smartphones, or watching TV.
The WHO says kids who spent too much time playing with smartphones may be at risk of attention problems.
The latest guideline comes amid growing research into the developmental effects of the widespread use of electronics by children.