Ribosomes convert mRNA into a protein. Ribosomes are small, membrane-less organelles that are significant sites of protein synthesis. mRNA (messenger RNA) holds a transcript or coding sequence for protein synthesis. The process in which ribosomes convert mRNA into a protein is known as translation. This takes place over three main steps – initiation, elongation, and termination. 

1. In the initiation phase, the ribosomal subunits assemble around the target mRNA strand and proceed to attract transfer RNA (tRNA) molecules bound to amino acids. The anticodon site of a special initiator tRNA interacts with a specific area on mRNA called a start codon. 
2. During the elongation phase, the ribosome moves along the mRNA molecule while linking amino acids to form a polypeptide chain. 
3. In the termination phase, the ribosome reaches a stop codon, which marks the end of protein synthesis. At this point, the ribosome releases the newly synthesized protein.