The Cry It Out (CIO) Method is a sleep training method that requires you to let your baby cry and fuss for a set period of time before you take any action to intervene and soothe them. It’s recommended that you wait until your baby is about 4 months of age, before trying out this method. There are both proponents and critics of the CIO Method. It can certainly work for some babies, but it may not be the best approach for others. When it comes to sleep training, it’s important to trust your parental instincts, try different methods and find what works best for you. Like so many things in parenting, there’s no one right way to sleep-train your little one.