Find the volume of $\displaystyle D= \left\{(x,y,z)\in R^3: z \geq y^2;\ y\geq x^2;\ x \geq z^2 \right\}$

I'm not quite sure where to start. Do I need to split D up into three different volumes? The body is symmetrical, so I would only need to calculate one of the three volumes in that case.

One of the three volumes is: $\displaystyle x^2 \leq y \leq \sqrt{z}$, but that doesn't really help me without any boundaries for y.