Using a historical perspective, this article describes how specific forms of documentation turned institutions of childhood into laboratories of child development. Drawing upon ‘laboratisation’ as an analytical concept derived from Science and Technology Studies, an arch will be traced from diaries kept by bourgeois fathers at the end of the 19th century to the scholarisation of childhood some one hundred years later, and on to ECE facilities at the start of the 21st century. This shows how institutions left their mark on individual children and, as laboratories of childhood, spread their institutional logic into broader areas of society by deploying practices and instruments of documentation.