scratch the surface
Investigate or treat something superficially, as in This feed-the-hungry program only scratches the surface of the problem, or Her survey course barely scratches the surface of economic history. This metaphoric term transfers shallow markings made in a stone or other material to a shallow treatment of a subject or issue. [Early 1900s]
Words nearby scratch the surface
scratch one's head,
scratch pad,
scratch sheet,
scratch someone's back,
scratch test,
scratch the surface,
scratch together,
scratch video,
scratch wig,
scratchboard,
scratchcard