essence; quintessence; spirit; soul; heart; pith (and marrow)
to the core; to the bone; (lit.) to the marrow
bone marrow; medulla; heart's core; depths of one's heart; main point; vital part
essence; kernel; spirit; pith
meninges; meninx; membranous coverings
marrow; pith; centre; center; bottom of one's heart
pulp (of a tooth); dental pulp