I feel like this should have a simple answer, but I can't find it.

I have 2 POCOs:

public class Category
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Product
{
    public int Id { get; set; }
    public int CategoryId { get; set; }
}

Notice that there are no object references on either POCO. With Code-First, how do I make EF4 CTP5 define a relationship between the two database tables?

(I know this is an unusual scenario, but I am exploring what's possible and what's not with Code-First)