Inter-organelle membrane contact sites are sites of close apposition between the membranes of two distinct organelles which act as a domain for inter-organellar communication. Contact sites can form between many different organelles and are modulated by different types of proteins, including: (i) tethering proteins, (ii) functional proteins, and (iii) regulatory proteins, which can have overlapping roles and together help to maintain contact sites [50]. In addition, inter-organelle contacts have been linked to multiple functions, including: (i) metabolite transfer, (ii) regulation of organelle dynamics, and (iii) additional cellular processes allowing the maintenance of cellular homeostasis [45,52]. mtDNA, Mitochondrial DNA; ROS, reactive oxygen species.