Here's a link to a blog I wrote for Apeiron about the gene PPARGC1A that is largely responsible for regulating the growth of new mitochondria.
https://www.apeironcenter.com/epigenetics/healthy-mitochondria-with-epigenetics/
And, I love the picture that got made for the article I've copied below.
Update since I wrote that article, I've been experimenting with regular cold exposure, and its a pretty excellent little biohack. I'll do some posts about that in the future.