It's never too early to start investing for a child's future. A custodial account is an investing account created for the benefit of a minor. Under the Uniform Transfer to Minors Act (UTMA), you can open and manage this type of account until that minor becomes a bona fide, legal adult.
Any adult can open a custodial account for any child, but there can only be one child per custodial account. And the adult who opens it is responsible for managing it until that minor reaches the age of distribution for their state of residence. Any earnings (up to a certain amount) will be taxed at the minor's rate.
Open a custodial account