WordPress Multisite take data from sites to the principal site

Hi All,

I’m studying the possibility to take some data from the sites that we have in a wordpress multisite to the principal site, something like that:

siteprincipal.domain.com

site1.domain.com
site2.domain.com
…

I need to take the post and metas to the site1, site2, etc… to the siteprincipal, Which could be the best solution?

Thanks!