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".
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Cloudy with outbreaks of rain and strong winds too. The rain persistent and at times heavy over high ground.
After a mostly dry evening with a few scattered showers, cloud and outbreaks of showery rain will spread northeast through the night.
Tributes have been paid to former Wales international Mel Charles, who has died at the age of 81.