PRIMER When the mRNA is in the cytoplasm, it is recognized by factors and complexed with the ribosome, which is the place where the message is decoded and the protein is built up. We are rather fortunate because most of the players participating in protein synthesis are known at the 3-D level; thus, we can reconstruct all the steps of protein synthesis at the 3-D level. Some of the figures, especially the ones depicting the process of protein synthesis with the ribosome, are so stunning that I virtually feel I am there viewing the process first hand. For this spectacle to flow in the most comprehensive way possible, I selected a certain sequence for the presentation. First, I present the 3-D structure of the two major players in protein synthesis: tRNA (alone and complexed with aatRNA synthetase) and ribosome. The reader must become very familiar with both, especially with the ribosome. Even though we know the structure of the ribosome in high resolution, I first introduce its structure by showing a series of images from low to high resolution. This approach should enable the reader to understand the structure better. Having introduced the basic players, I proceed with the first stage of protein synthesis, the initiation. This is compared in both prokaryotes and eukaryotes, and the known 3-D structure of initiation factors and their interaction with rRNA are presented.