The contain microscopic structures called follicles which contain a potential egg cell and granulosa cells.

It seems like you've missed out on specifying the subject of your sentence. However, based on the context, it appears you're referring to the ovaries. The ovaries contain microscopic structures called follicles. These follicles house a potential egg cell, also known as an oocyte, and granulosa cells. The granulosa cells provide nutrients to the developing egg cell and secrete hormones necessary for the egg's maturation and release.