1. The problem is to simplify the expression $\frac{3}{3^2}$.\n\n2. Recall the rule for exponents: $a^m \div a^n = a^{m-n}$. Here, the numerator is $3 = 3^1$ and the denominator is $3^2$.\n\n3. Apply the rule: $$\frac{3^1}{3^2} = 3^{1-2} = 3^{-1}.$$\n\n4. A negative exponent means the reciprocal: $$3^{-1} = \frac{1}{3}.$$\n\n5. Therefore, the simplified form of $\frac{3}{3^2}$ is $\frac{1}{3}$.