X2 + 4x + 4

Step 1: Identify the given expression. The expression to be factored is $x^2 + 4x + 4$.

Step 2: Recognize the form of the expression. This is a quadratic trinomial in the form $ax^2 + bx + c$. We can check if it's a perfect square trinomial, which follows the pattern $(a+b)^2 = a^2 + 2ab + b^2$.

Step 3: Apply the perfect square trinomial formula. Compare $x^2 + 4x + 4$ with $a^2 + 2ab + b^2$: Here, $a^2 = x^2 \implies a = x$. And $b^2 = 4 \implies b = 2$. Check the middle term: $2ab = 2(x)(2) = 4x$. Since the middle term matches, the expression is a perfect square trinomial.

Step 4: Write the factored form. $x^2 + 4x + 4 = (x+2)^2$

The factored form of the expression is $\boxed{(x+2)^2}$.