The number of Golgi stacks in cells vary by the function of the cells, as does the number of cisternae that comprise each stack. The stacks are linked into a single complex by the tube-like connections between cisternae. Importantly, each end of a Golgi stack is distinct, which ensures that the process of molecule modification that occurs in the Golgi apparatus occurs in an organized, methodical manner. The cis face of a Golgi stack is located near the endoplasmic reticulum and is the end where molecules enter for processing. The trans face is positioned near the plasma membrane and is the face of the stack from which modified substances are shipped. The Golgi apparatus was tagged in the fox lung cells featured in the digital video sequences in this section with EGFP fused to a Golgi targeting signal. Mitochondria were visualized as well, through the use of a mCherry-mitochondrial targeting signal fusion tag.