As a process that brings together, in close proximity, two linear structures of considerable length (mRNA and the nascent polypeptide chain) and large protein factors (EF-G and aminoacyl-tRNA·EF-Tu·GTP ternary complex), protein synthesis poses a logistic problem of traffic control: how to guarantee uninterrupted, high-precision performance without steric interference and entanglement of the various ligands. Since cryo-electron microscopy (cryo-EM) visualization provided the first detailed three-dimensional (3-D) images of the ribosome, much work has gone into the mapping of tRNA and elongation factors bound to the ribosome at various stages of the elongation cycle. A recent study of a 70S ribosome carrying a genetically inserted tRNA-like RNA fragment furnished a higher-resolution (17-Å) map of the vacant ribosome, and the use of this new map in the subtraction produced a linear mass distribution covering the platform side segment of the mRNA path, as well as a mass hovering just at the entrance of the 30S subunit channel. tRNA bound to the ribosome has been directly visualized by 3-D cryo-EM in various tRNA-ribosome complexes. Visualization of the ribosome-bound tRNA is still a challenging task because the smallest dimension of the molecule is on the order of the resolution of cryo-EM and the occupancy of some tRNA binding states is intrinsically low.