# Chemistry and imaging on MiSeq

**Four-Channel Sequencing by Synthesis (SBS) Chemistry**

In four-channel SBS, bases are identified using four different fluorophores for each base and four images per sequencing cycle.

* The sequencing cycle begins with a chemistry step where all four deferentially labeled bases are added to the flow cell.
* Following nucleotide incorporation, the imaging cycle begins and includes the capture of four distinct images using four different wavelength bands.
* The images are processed with image analysis software to determine which nucleotides were incorporated at each cluster position across the flow cell.
* With four-channel sequencing, every sequencing cycle requires four dyes and four images to determine the DNA sequence.

The MiSeq and HiSeq Series Systems currently use four-channel SBS.\
![](https://761066130-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FGM9W2DuBTgEXv1ClCm8H%2Fuploads%2Fgit-blob-f484ed76cbee05797497ae681402ce677a4975ed%2Fimage1.png?alt=media\&token=b6d2b843-64ee-4d36-9ef4-f70e89a8942c)

For more information, see [SBS Technology Spotlight](https://www.illumina.com/content/dam/illumina-marketing/documents/products/techspotlights/cmos-tech-note-770-2013-054.pdf).

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