Today's census figures will focus on international migration, ethnic groups and religion - and the Welsh language.
Some parents like Rhian Cecil hope it'll lead to more Welsh medium and bilingual schools over the next ten years.
"It's really important for us as Welsh speakers to be stood up and counted".
"Hopefully all the figures can help local councils create more provision".
More top news
A cold night but temperatures remain above zero
Watch our report on events held to mark 'White Ribbon Day' - and access information and advice on domestic abuse and how to get help.
Outbreaks of rain will continue through the night, turning heavy in places