> For the complete documentation index, see [llms.txt](https://knowledge.illumina.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowledge.illumina.com/instrumentation/miseq-ruo/instrumentation-miseq-ruo-reference_material-list/000003757.md).
# 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.
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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