Think back to the first time you held a smartphone or tablet in your hands. For most adults, this probably happened later in life. Now, a new generation of kids is growing up exposed to screen time as toddlers, or even babies. What impact will this screen time have on their very young and still growing brains? Dr. Dimitri Christakis takes us inside his lab at the Seattle Children's Research Institute and demonstrates how he studies some very young research participants. Plus, Dr. Christakis sits down with CNN’s Chief Medical Correspondent Dr. Sanjay Gupta and shares his most realistic tips for setting screen time limits.