Improved measurement of the active ingredients that promote children's gains in early childhood education programs is a topic of considerable interest to stakeholders. Accurate and reliable measurement of early childhood education experiences can aid policymakers, school administrators and educators in improving the quality of early education and help parents make choices among early learning options. The Early Learning Network (ELN), a team of researchers from six institutions located across the United States and funded by the U.S. Department of Education's Institute of Education Sciences, is making strides in contributing to this knowledge base. Jointly, ELN team members took a multifaceted approach to direct observations of classroom processes. This brief explores some lessons learned from one approach: Fine-grained, time-based measures that capture how young children spend their time in prekindergarten (pre-K) and kindergarten classrooms. These measures quantify how much time individual or groups of children spend on different instructional and non-instructional activities, the content of instruction (e.g., literacy, math), the instructional format (e.g., whole group, small group, centers, individual), and in some cases, the frequency with which children experience certain types of dialogues with others (e.g., open-ended questions, multiple-turn exchanges).