Theophrastus Repository contains the majority of the scientific work performed in IMFE, in an open-access, digital form.

Its collections cover environmental information broadly, emphasizing mainly on Forest Research and secondly on environmental issues. Scholars have access in scientific articles, studies, reports, grey literature, photographs and maps.

Besides its scientific value, Theophrastus is considered part of the Greek environmental legacy as it depicts all the evolutions which took place in Greece due to mankind or nature itself, thus interpreting the evolution of ecosystems.