Hi, my girl is 7 years old.. she asked for cellphone. my question is, is the cellphone safe for children in this age?

Cellphone can be quite helpful. As to safe, that depends on you. You will have to teach her how to discriminate between health and dangerous activities. You will have to screen her activity to prevent predators. You will have to limit her time closely on the phone, otherwise she will get lost in it's seductiveness. 7 may be a bit too young, but if you are willing to supervise, the choice is yours

A cellphone will not cause brain tumors, but can still cause a significant amount of brain damage. A colorful screen with sounds and animations is designed to be appealing and can consume large portions of your child's work/play/study time, depleting time for interaction with the world, using large muscle groups, and interacting face to face with friends, siblings and adults.