Different genes in an organism are generally expressed through proteins which are synthesized through the information stored in genes. It is through these proteins that phenotype is eventually determined. There are, of course, some genes which do not express through synthesis of proteins, but are meant for the synthesis of different components of protein synthesis apparatus. For instance, there are separate genes for different transfer RNA (tRNA) molecules and also for ribosomal RNA (rRNA). These genes do not contain any information for the sequence of amino acids in a protein. In this section, a brief introduction about structure of proteins and an account of structure and biogenesis of the components of protein synthesis apparatus, particularly the transfer RNA (tRNA) and ribosome will be presented. In the next three topics, details of the mechanism of different steps of protein synthesis will be described.