2000 B.C.E.- the formation of Balto-Slavic linguistic family.
1500-1300 B.C.E. -disintegration of Balto-Slavic family followed by numerous languages changes characteristic for shape of future Slavic languages. The basic features of this period can be only approximately reconstructed by methods of comparative historical linguistics.
4th -8th centuries- migrations of Slavic-speaking tribes that will definitely divide Slavic languages into three groups: eastern (Russian, White-Russian, Ukrainian, Ruthenian), western (Polish, Kashubian, Lower Sorabian, Upper Sorabian, Czech, Slovak) and southern (Slovenian, Croatian, Serbian, Bosnian, Macedonian, Bulgarian, Church Slavonic).