Kroll's theory is one of the most significant on children's writing development. He proposed that children's writing development is split into 4 phases. Kroll explicitly states that these phases are 'artificial' in the sense that the boundaries between the phases are imprecise and he recognises that each child is different, thus their development is unique. The phases of writing development have been highlighted to give the reader a broad outline of what phases a child goes through during writing development; however when studying an individual's development in depth, the phases may be disregarded to an extent.