Firelight Heritage Farm Publishing is based in the United States.
Microgreens are really just overgrown sprouts, and can be grown from any clean seed for any kind of green that you'd normally eat mature, and a few that you would not! They can be grown like sprouts, with just water, or in soil. Either way, they are allowed to get a little larger than sprouts, but usually not fully into the secondary leaf stage. Unlike sprouts, Microgreens are typically clipped rather than tossed in roots and all. They'll grow in a sunny window just fine. You can find Microgreen mixes and seeds in most major seed supplier catalogs and websites now.