Do you know how much time your kids spend on their mobile devices and what they're doing when they're using them? There's no need to guess. There are products, apps and services that enable you to monitor and manage their screen time.

It all starts with creating an account for your child. If he or she is under 13, you can create a child account, which gives you control over your child's device from your own device.

For iOS devices, this gives you the ability to require your child to ask permission before downloading apps and making in-app purchases (all other parental controls are set up on your child's iOS device).

For Android devices, when you set up your child's account through the Family Link app (free for iOS and Android), you have access to all parental controls from your own device.

At age 13, Apple or Google gives them the option to manage their own account. If your child chooses to manage his or her own account, parental controls will be limited to those that you set on your child's device.

Most of the parental controls for iOS devices reside on the device. So even when your child takes over managing their own account, most of the parental controls remain in place. Find on-device parental controls at Settings > General > Restrictions. You'll be prompted to create a parental PIN code and all future changes require inputting the parental PIN code.

Android users can use the FamilyLink app. Content settings are set in the Google Play app > Settings > Parental Controls.