The Stay Cool study is a follow-up of children who previously participated in the STAARS study during their infancy and toddlerhood. In the study, we measure self-regulation whilst participants complete play-based and child-friendly activities. We take a multimodal approach, using neuroimaging, physiological, and behavioural measurement techniques to explore self-regulation within the mind, brain, and body. Many of these measures are similar to the ones used in the STAARS study e.g., EEG, fNIRS, eye-tracking and standard tabletop and screen based tasks.