An ice nucleating particle INP is operationally defined as an atmospheric aerosol particle upon which ice grows when it is exposed to appropriate cooling and supersaturation with respect to water (or ice). Our two INP counters FINCH and FRIDGE apply two independent experimental approaches to meet these conditions. FINCH is a continuous flow reactor that exposes a sample of atmospheric aerosol for approximately 8 seconds to the appropriate conditions and counts the emerging macroscopic ice crystals optically. FRIDGE measures the INP that were previously extracted from air onto a substrate offline on a cold stage.