New Post: Nested Regions

Hi,
I'm using Prism-Mef, i have RegionB which is nested inside RegionA
When i declare:

 IRegion regionB= regionManager.Regions[RegionNames.RegionB];

i got the exception:

The region manager does not contain the RegionB region.

1-How i can access RegionB to Add view to it, knowing that i will use it as a scoped region.
2-If i have a third level of nesting: for example RegionC which is nested inside RegionB, how can use RegionC to add a View

Thanks in advance.