Abstract. The aim of this thesis is to implement a web application for presenting changes recorded in multiple versions of microRNA databanks. The application has been integrated into the DIANA web application toolkit, which is a set of tools for analyzing microRNA data, and has been developed in cooperation with the research center “Alexander Fleming”. MicroRNA molecules constitute an important branch of biological research, since their function is correlated with gene expression, and thus, microRNAs are related to diseases and treatments. As new data emerges from research concerning these biological molecules, new versions of databases recording them are issued. It is possible that recorded data differs between various versions of these databases. As a result, there can be difficulties in research, since a researcher cannot have a complete overview of all recorded knowledge concerning a specific microRNA. The aim of this thesis is (i) to implement a database containing information about the evolution of microRNA data recorded in the mirbase archives (www.mirbase.org) and (ii) to implement a web application that presents evolution graphs for recorded microRNA data.