How does yellow marrow convert to red marrow?

[Bio-Hazard]

I keep reading that it's possible, but I don't understand how.
How does fat turn into hematopoietic tissue????

I'm thinking that I'm missing something here.
I tried finding some kind of articles, but I didn't get much information back.
Supposedly, it's possible, but I don't get it.

The only thing I can think is that it supplies the nutrients for genesis and that's about it. Am I wrong?