What is an example of symbolism in Romeo and Juliet act 2, scene 2?

The symbol of poison introduced by Friar Laurence in act 2, scene 2, has great significance in Romeo and Juliet. As the good Friar introduces us to his little bag of potions, he comments somewhat ominously on how poisons aren't intrinsically evil, but only made so by the uses to which they are put.
As well as foreshadowing the Friar's own use of the sleeping draught he prepares for Juliet, this remark introduces poison as symbolizing society's seemingly inordinate capacity to destroy the good things of life, with potentially damaging and tragic consequences. The most obvious example of this would be the way in which society turns something sweet and pure—the love between Romeo and Juliet—into deadly poison that destroys them both. No one deliberately set out to do this, of course, any more than Friar Laurence intended to hurt Juliet by giving her the sleeping potion; but it's how things have turned out all the same.