This book is suitable for pupils to assess and learn subitizing skill. It is particularly useful for preschoolers and remedial pupils. Subitizing means instantly recognise “how many” in a small set without counting. Subitizing skill is one of the pre counting skills that young learners should learn before they proceed to learn rational counting and it is a necessary component for the mapping of number words to numerical magnitudes. In this book, we assess pupils' subitizing skill in the first section. Then in the second section, we propose a four-stage sequence to acquire subitizing skill.