Explore a differential of volume in spherical coordinates. [math]dx dy dz = \rho^2 \sin \phi d \phi d \theta d \rho [/math] The red brick shown has its outerface contrained to lie on the unit sphere, but you can manipulate the brick's other boundaries, its min theta and max theta, its min phi and max phi, etc. Play with this sketch as you learn your way around a spherical coordinate system.