1
general::
Pay a brief visit, as in I'm just going to look in on Gail and the new baby; I won't stay long. [c. 1600] Also see LOOK SOMEONE IN THE FACE. look into Also, see into. Investigate, as in He promised to look into the new law, or We must see into the matter of the missing checks. The first term dates from the late 1500s, the variant from the mid-1800s.
American Heritage Idioms