Christianity throughout the 2nd and 3rd centuries generally has been less studied than that of the periods that came before (Apostolic Age) and after it (First seven Ecumenical Councils). This is reflected in that it is usually referred to in terms of the adjacent periods with names as such "post-apostolic" (after the period of 1st century formative Christianity) and "ante-Nicene" (before the First Council of Nicaea). The 2nd and 3rd centuries were, however, quite important in the development of Christianity.