This is my first participation, and I thank in advance all of you who will try to help me here. As I asked in the title, is it correct to say "the core" or "the nucleus" of an exhibition? I mean a group of specific items presented in an exhibition. It is not a section, which I think is something more general and in which may exist different "nuclei". The use of the word "nucleus" here comes from a direct translation from the Portuguese, "um dos núcleos da exposição", for instance.
Thank you all again, Isabel