It is well documented that children around the world develop biases based on ethnicity and race. Children come to represent the socially constructed notions of ‘ethnicity’ and ‘race’ as relevant categories for making predictions about individuals, interpreting ambiguous evidence, and making friendship choices. These early developing biases give rise to racial/ethnic prejudices that persist into adulthood and cause harm to individuals and communities through discrimination, social exclusion, and violence. Therefore, it is critically important to understand not only how ethnic/racial biases develop during childhood, but also how they can be changed with experience and learning. Working Group 2 within the Collaboratory Against Hate aims to bring together a diverse group of researchers (with regards to research expertise and methods of inquiry, as well as lived experience) to tackle this important issue.