Child development experts are urging Facebook to remove its new messaging app designed for kids. In a letter sent recently to Facebook CEO Mark Zuckerberg, the group of experts argue that young children are not ready to have social media accounts or online relationships. Facebook launched the free Messenger Kids app in December. The app is meant for children under the age of 13. Facebook says the app provides a way for children to chat with family members as well as friends that their parents have approved. The app does not give children their own Facebook or Messenger accounts. Instead, it is connected to a child’s parent’s account. Facebook has said the app fills “a need for a messaging app that lets kids connect with people they love but also has the level of control parents want.” But critics say the app is a way for Facebook to bring in younger users before they choose another popular social media messaging service.