Physiology Understanding (PhUn) week is an ongoing effective outreach program of the American Physiological Society. This annual event for K-12 students is held every November. During PhUn week, students get to meet a physiologist and perform science activities. This past year a small private parochial school contacted me and asked me to come into the third grade class in January. The event started with an introduction to the job of a physiologist and an explanation of heart function. The students created their hypothesis Exercise increases heart rate and planned their experiment. The correct way to measure heart rate via the carotid artery was demonstrated by the physiologist and students took their baseline heart rate. Then together with their partner the students went outside to perform their experiment. There was fresh snowfall on the playground yet the students were undaunted to perform the exercise portion of the activity. One member of the student pair ran for three minutes around the perimeter of the playground. Upon stopping they measured their heart rate. The second member of the pair repeated the exercise and took their post exercise heart rate. The whole class went back into the classroom to discuss their results. A discussion was held and students stated their data from before (baseline) and after exercise. The students agreed that their data supported their hypothesis. The physiologist explained why the heart rate needs to increase with exercise. It is always a thrill to be able to work with young students and be the first scientist they have ever met. This PhUn week event is certain to create a lasting memory for both physiologist and students alike.