How to factor these monomials?

Question

This is the original problem: $x^3+x^2y+xy^2+y^3$

Answer: $(x+y)(x^2+y^2)$

I understand that the answer is correct, but I can't figure out how to get to it.

Answer 1

$$\underbrace{x^3+x^2y}_{\text{Group these two}}+\overbrace{xy^2+y^3}^{\text{Group these two}} = x^2(x+y) + (x+y)y^2 = (x+y)(x^2+y^2)$$