RNA must be shipped on dry ice, unless the RNA is precipitated in ethanol. Tissues / cell cultures must be flash frozen in liquid nitrogen or dry ice and have to be shipped on dry ice. Alternatively, fresh material can be stabilised in “RNAlater” (e.g., Ambion, SIGMA or QIAGEN) and be sent at room temperature. Please verify in advance that the couriers you are using accept dry-ice shipments.