Top Compartment consists of sharp metal pins. The lid is held on by a surprisingly strong magnet. There are holes drilled in between the cutting pins to allow the ground herb to fall through to the second compartment. Because of this, the herb keeps a consistency necessary for good rolled joints.
The second compartment has a fine micron screen mounted to the bottom of it. This screen allows the THC from the ground herb to fall into the third compartment. If you shake the grinder around while the herb is still in this compartment, more THC will gather in the third compartment.
The third compartment is a thin tray. The first time you open the Space Case, there is a tiny triangle piece of plastic which is used to gather any fallen THC on this tray. It takes a few grams of high quality herb to build up a small amount of THC in this compartment.