How to multiply objects?

Hi everyone,
I’m trying to create a lipoprotein that looks something like this: http://content.answers.com/main/content/img/oxford/Oxford_Sports/0199210896.lipoprotein.1.jpg
except as a solid sphere.
As you can see, the phospholipids consist of a lot of repetitive spheres. I was wondering how I could duplicate an object once I make it.

Any help would be appreciated. Thanks!

you can use the array modifier which i use a lot to make stone wells and such, here is a tutorial i found on youtube