It narrows a location down further, you still need to know inside where and you only need to specify if that location actually has an interior.
Inside nucleus
the location of neutrons (along with protons) is inside the nucleus.
In is inside somewhere or something, At is at a location, but doesn't indicate inside or outside
Ideally inside.
Inside you body ;)
It's the fluid inside cells.
Inside of your veins and arteries.
Inside the alternator.Inside the alternator.
If it is the one I'm thinking of (the underground pool location) then you have to be a member to get inside.
Inside the alternator
It is located inside the cell.It can be any where in cell.
Inside the alternator.