At this point in Scene 7, Laura and Jim are alone in the Living Room and she is face to face with her high school crush. This moment is truly a holy moment for Laura, she worshiped Jim O'Connor in silence, to her he is a god. This man, Jim O'Connor, is the only man Laura has ever had feelings for in her life, she is 24 years old and is made to feel like a high school girl again by getting the chance, she never had in high school, to talk to the boy, now a man, she adored from afar.
Laura gets Jim to autograph her high school program from his play. These simple events have given Laura more joy than anything else she has experienced.
The quote refers to how Jim O'Connor, the gentleman caller has made Laura feel on this very special night. She is filled with happiness, glowing with joy and smiling. She is so happy and relaxed with Mr. O'Connor that she shows him her favorite glass animal, the unicorn, a symbol, in itself for Laura, who like her is not like everybody else, all the other horses, he has a horn which makes him different, just as Laura has a limp.
Laura shows Jim the unicorn exclaiming:
"There now you're holding him gently, hold him over the light, he loves the light! You see how the light shines through him?" (Williams)
Just as Laura has lit up with joy being with Jim, the unicorn, made of glass, sparkles when it is held over the light. In the glow of the candlelight the little glass unicorn looks beautiful, refracting the light into many colors. Laura is also beautiful in the candlelight, sitting next to a man she still has deep feelings for, she is brought into the light of love by Jim.
Symbolically, Jim leads Laura out of the darkness, of having never been kissed, or considered attractive by any man, he brightens her life, even if it is only for one short evening.
The glass menagerie is symbolic of all the characters because each of them is fragile in his or her own way. Laura is frail and shy. Amanda has had her life shattered by her husband who abandoned her. Tom feels trapped, like one of Laura's animals in her collection, he longs to escape the controlling hand of his mother.