Nested Collections

Hi All

from a laymans perspective is nested collection refers to obtaining data from two different collections (collection1,Collection2) into a resulting collection (Collection 3)/data item.

Can some one help me out with a good example or a link where i can find detailed explanation about nested collections .
A nested collection is a collection with one ore more collections in it. I encounter these when I get data back from a JSON service (I convert the JSON to a collection). The initial collection is like the web response. The sub-collection will be the array of JSON data. (This is just an example - not all nested collections are from JSON data).
You set up a loop to go through the first collection (collection1). You can either copy the the sub-collection from collection1 to a collection, or can have another loop go through the sub collection. If you have even more sub-collections, you would use loops to access them as well.