When estimating, children perform much more complex mental activities than when counting. Estimation teaches relationships between various quantities and develops logical and spatial thinking as well as cause and effect analysis. By experimenting with Korbo blocks as concrete objects, children develop their intuition related to measurement and the ability to estimate its result. Thanks to this, the child gains skill in determining “by eye” e.g. distance, mass or quantity, which will pay off in life situations requiring such skills.