The 10x™ GemCode™ Technology samples a pool of ~3,500,000 barcodes to separately index each cell's transcriptome. It does so by partitioning thousands of cells into nanoliter scale Gel Bead In EMulsions (GEMs), where all generated cDNA share a common 10x Barcode. Libraries are generated and sequenced from the cDNA and the 10x Barcodes are used to associate individual reads back to the individual partitions. To achieve single cell resolution, the cells are delivered at a limiting dilution, such that the majority (~90 99%) of generated GEMs contains no cell, while the remainder largely contain a single cell. Upon dissolution of the Single Cell 3' Gel Bead in a GEM, primers containing (i) an Illumina® R1 sequence (read 1 sequencing primer), (ii) a 16 nt 10x Barcode, (iii) a 1 2 nt Unique Molecular Identifier (UMI), and (iv) a poly dT primer sequence are released and mixed with cell lysate and Master Mix. Incubation of the GEMs then produces barcoded, full length cDNA from poly adenylated mRNA. Afte r incubation, the GEMs are broken and the pooled fractions are recovered. Enzymatic Fragmentation and Size Selection are used to optimize the cDNA amplicon size prior to library construction. R1 (read 1 primer sequence) are added to the molecules during GEM incubation. P5, P7, a sample index, and R2 (read 2 primer sequence) are added during library construction via End Repair, Atailing, Adaptor Ligation, and PCR. The final libraries contain the P5 and P7 primers used in Illumina bridge amplification.