What causes cell differentiation during an organism's development?

The specialization of cell in its broad sense,growth also include the phase of cell development

The truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey