The coldest part of a CoolSculpting treatment is the gel pad that is applied to the skin prior to application of the cooling device.  Oddly, while this gel pad is at room temperature it feels ice cold.  The purpose is to protect the skin from frostbite.  Once the cooling device is applied it feels cool but not cold for 5-10 minutes.  Then the nerves become desensitized and you feel nothing at all.  The 2-minute post-treatment massage is the most uncomfortable part of the CoolSculpting treatment but most people feel this is quite tolerable.