I understand that when you create a clustered index, SQL Server doesn't create a physical structure seperate from the table.
Initially I though that this can't be right because SQL allows you to create a table in one filegroup and then create the Clustered index in a different filegroup. I tested this and saw that when you create a Clustered index on a table in a different filegroup, SQL moves the table to the filegroup that contains the clustered index.
My question> Why is it that after creating a clustered index, the size of the table increases slightly? Is this perhaps the pages in the non-leaf levels of the B-Tree?