A kief catcher, also known as a pollen catcher or kief screen, is a feature found in some grinders and herb mills specifically designed to collect and store the kief or trichomes that separate from the cannabis buds during grinding. It is a separate chamber or compartment located at the bottom of the grinder.

The purpose of this is to collect the valuable trichomes that contain high concentrations of cannabinoids, terpenes, and other compounds responsible for the potency, aroma, and flavor of cannabis. The kief catcher typically consists of a fine mesh screen or series of screens with tiny openings that allow the trichomes to pass through while retaining the larger plant material.

As cannabis buds are ground in the grinder, the trichomes are dislodged and fall through the screen into this. Over time, the accumulated kief forms a powdery and potent substance that can be collected and used separately.