Example of one method for performing next generation sequencing: Illumina SBS (Sequencing by Synthesis). Repeated amplification of fragments of sample DNA occurs as shown in (A): steps 1–10. This series of steps takes place on hundreds of millions of attached adaptors (adaptors A, B), providing “depth”, ie, the “x-fold” of NGS. In (B) one or both strands are sequenced as shown, ie, sequenced by synthesis.