Where can I buy espresso?

I have a espresso machine at home, but I have no idea where I can buy espresso. I know all it is a finely ground coffee beans but where can I buy that? Do regular grocery stores carry it. I live in Atlanta so we Have Kroger, Publix, and Whole Foods. Please help!!! It would save me a ton of money considering I go to Starbucks every morning. :) Thanks!