1. **State the problem:** Simplify or factor the quadratic expression $y^2 + 8y + 16$. 2. **Recall the formula:** A quadratic expression $ay^2 + by + c$ can be factored if it can be written as $(y + m)(y + n)$ where $m$ and $n$ satisfy $m + n = b$ and $mn = c$. 3. **Identify coefficients:** Here, $a = 1$, $b = 8$, and $c = 16$. 4. **Find factors of $c$ that add to $b$:** We look for two numbers $m$ and $n$ such that $m + n = 8$ and $mn = 16$. 5. **Check possible pairs:** $4 + 4 = 8$ and $4 \times 4 = 16$. 6. **Write the factorization:** Therefore, $y^2 + 8y + 16 = (y + 4)(y + 4) = (y + 4)^2$. 7. **Final answer:** The expression factors to $$(y + 4)^2$$.