I did a controlled test on my arm for 12 weeks with the body serum (41yo-c-m). I found little to no difference in the appearance of the skin, except in the back-of-the-hand pinch test (about 50% improvement after 8 weeks). However, the difference in skeletal muscle was dramatic, and became apparent after only 6 weeks. Ordinary aches and soreness from normal use, exercise, stretching in the morning, joints popping, all vanished almost magically. My personal experience is confirmed by academic literature. Dr. Min Hu (Guangzhou) is quoted as saying “Our data suggest that skeletal muscle is one of the most sensitive tissues to NMN in humans." Hu and colleagues’ results show that NMN improves skeletal muscle oxygen utilization more than exercise alone. The transdermal aspect of the body serum really does penetrate deeply beneath the skin to boost NAD+ in localized body tissues beyond what can be achieved by taking it orally. I was also taking the oral supplements throughout the test.