Maria Montessori opened the first Casa dei Bambini (Children's House) in a low-income housing project in Rome. This marked the beginning of her practical application of the Montessori Method with typically developing children.

Montessori meticulously observed the children in the Casa dei Bambini, refining her educational materials and techniques based on their natural learning behaviors. This period was crucial for the development of the Montessori Method.

Montessori published her first book, 'Il Metodo della Pedagogia Scientifica Applicato all'Educazione Infantile nelle Case dei Bambini' (The Montessori Method of Scientific Pedagogy Applied to Childhood Education in the Children's Houses). This book outlined her educational philosophy and practical methods, gaining international attention.

The Italian book was translated into English and published in the United States under the title 'The Montessori Method'. This made her theories available to a much wider audience, further contributing to the international growth of her educational approach.

Montessori schools began to open rapidly in Italy and around the world, reflecting the growing interest in her innovative educational methods. This period marked the beginning of the Montessori movement.