NUK First Choice Learner Bottle with Temperature Control indicates when the desired drinking temperature is achieved, providing assurance the drink is not too hot. When the temperature is too hot, the indicator changes from its usual blue to white. Desirably, the liquid should have body temperature (37 °C = medium blue). It should be noted that Temperature Control is only an aid, therefore, the temperature should be checked a second time prior to offering the drink to the child.