Here's why:
* "Invisible children" is a figurative term. It refers to children who are marginalized, ignored, or forgotten by society. They might be experiencing poverty, displacement, abuse, or other forms of hardship that make them unseen.
* There is no way to count them accurately. The concept of "invisibility" is subjective and depends on the individual's perspective.
* The phrase might refer to a specific organization or campaign. "Invisible Children" is a non-profit organization that focuses on raising awareness about the conflict in Uganda and supporting children affected by it.
If you're interested in learning more about marginalized children or specific initiatives related to this concept, I'd be happy to help you find resources.