Apparently, a female medical student is performing some chemistry in front of a female professor.  Both are in lab coats.  The professor is waiting for this session to be over while the student is busy getting the right mixture, hoping it does what she wants it to.  Both are tired and want to return to their beds but know they have a long day ahead of them.  After the session is over, the student will leave to meet a friend for dinner, and the professor will likely do the same.
