What Is This Garden Plant?

I recently started a garden of veggies and fruits with my daughter. We have peppers, green beans, tomatoes, and cucumbers. The garden was made by my father-in-law and we put Miracle Gro fruit and veggie soil in the large plastic container. Now I have a plant I'm not sure what it is. I'm thinking it's a weed, but don't want to get rid of it if it isn't. Do you know what this is?