marrow - noun

the fatty network of connective tissue that fills the cavities of bones

any of various squash plants grown for their elongated fruit with smooth dark green skin and whitish flesh

very tender and very nutritious tissue from marrowbones

large elongated squash with creamy to deep green skins

the choicest or most essential or most vital part of some idea or experience

marrow - thesaurus

center   centre   core   essence   gist   heart   inwardness   kernel   meat   nub   pith   substance   sum