Endosomes are a heterogeneous population of intracellular organelles responsible for
sorting, recycling, or transporting internalized materials for degradation. Endosomal
sorting and maturation are controlled by a complex interplay of regulators, with RAB
GTPases and phosphoinositides playing key roles. In this decade, another layer of
regulation surfaced with the role played by membrane contact sites between the endoplasmic
reticulum (ER) and endosomes. Specific regulators of ER-endosome contact sites or proteins
localized at these sites are emerging as modulators of this complex endosomal ballet. In
particular, lipid transfer or recruitment of various complexes and enzymes at ER-endosome
contact sites play an active role in endosome sorting, scission, and maturation. In this
short review, we focus on studies describing ER-endosome contact sites in these three
endosomal processes.