Trained as a systems physiologist, I am most interested in regulatory mechanisms, and particularly regulation involving the neurotransmitter serotonin (5HT) during postnatal maturation. Currently I study maturation of motor systems in infant mice. To date I have collected extensive baseline information on the maturational patterns of some 15 motor activities and simple reflexes. Some of these, such as righting reflexes and simple withdrawal reflexes, are essentially mature at birth, while others mature at various ages during the first postnatal week through weaning at 21 days postpartum. Over the same time span, locomotion matures from primitive swimming movements restricted to the forelimbs, culminating in adult gait, grooming and escape activity. The maturation of the cerebellum is almost entirely postnatal in mice. The architecture of the cerebellar cortex is perhaps one of the best-described for a complex region of the brain, including phylogenetic studies from lamprey through primates, and maturational descriptions for mice. This elegant system of circuits matures over the same postnatal time span when new motor behaviors are appearing. I am applying digital video to reveal details of the movements and possible relationships with cerebellar maturation.