Valid feedback is essential for the administrators, educators, parents and, of course, for children to be able to steer their development in a sustainable way. Key influential theorists such as Montessori, Piaget, Vygotsky, and others all used observations extensively to understand how children learn and use knowledge about children's learning to improve pedagogies and children's lives. However, most adults including teachers in the ECEC settings have not always observed children and tracked their growth. Based on the research and professional development programs conducted in Finland, Taiwan and Hong Kong with more than 100,000 observations, we found some relationships between young children's involvement, adaptation and agency in early childhood settings through systematic observations. We will introduce observation strategies with video clips and demonstrate our latest mobile application for observation for practitioners to contribute to a big data pool aimed to enhance the teaching quality in ECEC settings. Copyright © 2018 EARLI.