When a client becomes more comfortable with interoceptive exposure, we can start talking about in vivo exposure. Again, we create a hierarchy from least to most distressing, and walk through this in session with them to collaborate on that structure.
Building a Hierarchy
Sometimes when people go out into the world and practice exposures, they find them less or more distressing than expected. Or they might find that the planned order of the hierarchy is inaccurate based on real world experience. So it can be adapted as you go along.