Applications open today for Mayor Bill de Blasio's "3-K For All" program.

Over the next three years, officials say it will roll out in four more areas, including Harlem, Bedford-Stuyvesant, Washington Heights and Central Bronx.

The program builds on the success of "Pre-K For All."

It expands free early childhood education to three year olds.

"Some kids got to really maximize, some kids got to really find their whole potential early, because those families happened to have the money to pay for programs.," the mayor said. "Other kids didn't get that opportunity."

By Fall of 2021, the city hopes to support 19,000 more 3-K seats across 12 school districts.

To apply, visit the city's web site.