Fifteen years have passed since the sociological profile of our periodical 'Borderlands. Social Studies' was established. Since 1992, when the journal first appeared, borderland studies have become an important trend of theoretical investigations and sociological research carried out not only by the research centers in border regions of Poland but also by many other academic centers across the country and Europe. Apart from sociological studies the borderlands which are defined from varied perspectives and to which varied meanings are given, became the area of research for a number of other disciplines: economics, pedagogical studies, history, cultural anthropology, arts and architecture etc. This means that borderland problems took inter- and trans-disciplinary shapes. Such situation, in turn, demands defining sociological specificity of borderland studies as well as working out common categories and approaches. In author's opinion, within the area of the sociology of borderlands there is room for at least five theoretical categories closely connected with one another as well as several others which derive from the former. Apart from the category of 'borderland' we should also introduce 'borderlandness', if such a neologism can be accepted. Analogically, apart from 'trans-borderland' we need the category of 'trans-borderlandness'. A category that connects problems of borderland and borderlandness functioning on both sides of the borders is the institution of border (boundary, frontier) and border checkpoint creating what we call the trans-border and transborderness. Derivative notions are, for example, national, ethnic and regional groups, religious community, social identity, national and ethnic relations, multiculturalism, democracy and private, local or regional homelands (Heimat) and sociocultural space of myself and that of my group. We invite to our periodical all authors interested in borderland studies, both from Poland and other European countries. We address this invitation particularly to young scholars, willing to research these problems individually or collectively. The periodical is open to authors who represent Belarussian, Ukrainian, Russian and Lithuanian borderlands, with hope that our common efforts will broaden the knowledge on trans-borderlands shaping the reality of both Poland and its neighbours.