Both stress systems have measurable outputs, including hormones like adrenaline and cortisol. Cortisol can be measured in saliva. Using decades of research, we have indicators of healthy cortisol levels in infants, young children, adolescents and adults. Tracking stress system biology is done routinely as part of research studies. However, the means to track healthy stress system development outside the research environment requires significant adaptation of available technology. See our 'About' page to learn what is required to make a stress system monitoring tool useful.