The first 5 years of life is a key period of development – not only do children grow at the fastest rate in their lifetime, they also develop a vast range of new skills and abilities. In this study, we are interested in some of the most important skills that children develop during this period, including language skills, the ability to quickly understand and react to new information, and the ability to concentrate and adjust behaviour in everyday life. Alongside this, we are interested in how the brain develops and allows children to learn all these new things, and, in turn, how new experiences may lead to changes in the brain. To do this, we will see the same children in the lab for assessments at multiple time points between 6 months and 5 years. Participating families will be recruited from the ALSPAC sample, meaning that the study children’s parents (i.e., the ‘Children of the 90s’) will already have participated in many assessments themselves (since their own childhood). This gives us useful information about the parents and their background, which will help us understand more about how their children develop. At the final time point (when children are 5 years old), we will look at how development of the brain and the key cognitive skills prepare children to start school, with the ultimate aim of understanding more about why some children struggle in school, either academically and/or socially.