We do a great deal of research on the hormone cortisol. This hormone is involved in the energy balance of our body and helps us respond to stressful situations. We often measure cortisol in saliva or in hair. If you participate in one of our studies, you may be asked to collect saliva in a special tube which we will give you. We may also ask you to collect saliva from your child. For this we use special small sponges that are very absorbent (see photo). Our experience with this method is that babies and young children do not find it annoying and even find it fun to suck on these sponges.