It is devoted to the anniversary of bestseller of the 20th century - book by K.I. Chukovsky “From Two to Five” which had several dozen editions. This is a long-term writer’s study of the features of children’s thinking and speech, literary essays, revealing the possibilities of children’s creativity, advice of an experienced writer to those who compose works for children. Material on children’s speech for the book K.I. Chukovsky collected from scientists and writers, from teachers and doctors, from specialists and ordinary citizens of the country from different geographical places and from different social groups. The writer concluded about the linguistic genius of babies. The methods used by preschoolers in the development of their native languages are imitation, the search for patterns, the establishment of causes and effects, the classification of speech units, the analysis of someone else’s speech, comparison, generalization and others. We present many examples of children’s speech from the book by K.I. Chukovsky, give the scientific and methodological justification of children’s word creation, folk etymology, criticism of the language of pre-school children. The advantages of six chapters of the philological research are noted. We cite the scientists’ statements about the children philological possibilities, show the task of educators for the speech development of pre-school children.