The region of the ER studded with ribosomes is termed the rough endoplasmic reticulum. The ribosomes are responsible for assembling amino acids into protein units to be sent into the rough ER for additional processing. When the proteins are ready they are either sent to regions of the cell where they are required or transported to the Golgi apparatus for additional modification. The majority of the proteins exiting the endoplasmic reticulum are exported in vesicles that bud from the smooth portion of the ER, which is typically significantly less extensive than the rough ER. The endoplasmic reticulum was visualized in the pig kidney cells appearing in the digital video sequences in this section with mEmerald fused to an ER targeting signal. The nucleus was simultaneously highlighted with mApple fused to H2B histones.