Apicomplexan parasites invade the host cell in an active process that involves gliding motility, formation and movement through the moving junction (MJ) and establishment of a prasitophorous vacuole (PV) around the parasite. In order to invade the host cell they employ an arsenal of virulence factors derived from the specialised secretory organelles; the micronemes, rhoptries and dense granules that are sequentially secreted during the invasion process.While the content of the secretory organelles has been well described and individual virulence factors have been the focus of research, our knowledge on the evolution, biogenesis, maintenance and regulation of these unique organelles is incomplete. Our recent research has established endosomal-like compartments as a key organelle for the specific sorting to micronemes and rhoptries.The goals of this research project are to i) Analyse biogenesis and segregation of endosomal-like compartments during parasite development within the host cell, ii) Analyse the content of endosomal-like compartments, iii) Systematically dissect the pathways involved in the organisation of the endosomal-like compartments and therefore in the biogenesis, maintenance and regulation of micronemes and rhoptries and iv) Compare the function of identified key factors in other apicomplexans, such as Plasmodium falciparum, the causative agent of malaria.The evolution of these specialised secretory organelles as an adaptation to an intracellular life style is not only a fascinating, unique feature of apicomplexan parasites that deserves detailed characterisation, but will lead to the identification of novel pathways and interference with these will also represent a new treatment option against these pathogens.