The Problem:
When we add a Solidify modifier to a hollow tube to give it thickness, it looks excellent in Object mode but seems to be missing vertices when you switch to Edit mode. If we start with an empty tube:
We want to give it some thickness, so we add a Solidify modifier:
Notice, there are no vertices on the outside radial edge! So if we wanted to edit the outside surface, what would we select if there are no vertices?
In Blender, every object consists of faces, lines or curves with vertices at each end. So does this mean that this tube is somehow corrupted?
Answer:
No, the tube is OK. It’s just that it has not yet been completed. We need to jump back into Object mode 
and apply the modifier before we can access any vertices that it creates:
Now if we jump back into Edit mode this is what we get:
So always remember – while the idea of using modifiers is to work non-destructively as much as possible – if you need to access the underlying geometry, you have to apply the modifier first.
