Prove that $\displaystyle |\mathbb{N}^{\mathbb{N}}| = |\mathbb{N}^{\mathbb{N} \times \mathbb{N}}|$.

I know of a fact that $\displaystyle |\mathbb{N}| = |\mathbb{N} \times \mathbb{N}|$. The problem here is how I can go about establishing the bijective function non-trivially.

Thanks in advance.