Illumina is the dominant company in DNA sequencing, making the machines, chemicals, and software that read genetic code. If your DNA has been sequenced for any reason, whether a prenatal screening, a cancer test, or a research study, there’s a better than 90% chance an Illumina instrument did the work. The company holds more than 90% of the clinical genomics testing market, making it one of the most quietly influential companies in modern science and medicine.
How Illumina’s Sequencing Technology Works
Illumina’s core technology is called sequencing by synthesis. The basic idea: read DNA by watching it get built, one letter at a time.
First, a DNA sample is broken into small fragments, roughly 500 base pairs long. Short adapter sequences are attached to both ends of each fragment, acting like molecular handles. These fragments are then spread across a glass slide (called a flow cell), where they anchor to the surface and get copied millions of times through a process called bridge amplification. This creates dense clusters of identical DNA copies, each bright enough for a camera to detect.
Then the actual reading begins. In each round, the machine washes four types of specially modified nucleotides (the A, C, G, and T building blocks of DNA) across the flow cell. Each type carries a different fluorescent color. Only one nucleotide attaches to each growing DNA strand per round, and a built-in chemical block prevents the next letter from being added until the machine takes a picture. A high-resolution camera records which color appears at each cluster location, identifying that letter. The block is then removed, and the cycle repeats. Modern Illumina instruments run this process for 300 or more rounds, reading sequences hundreds of letters long across billions of clusters simultaneously.
From Sample to Sequencer: Library Preparation
Before DNA can go into an Illumina sequencer, it needs to be prepared in a specific format called a sequencing library. This involves three main steps: breaking the DNA into small pieces, cleaning up the ends of those pieces, and attaching the adapter sequences the machine needs to recognize them.
Fragmentation can be done mechanically, using sound waves to physically shear the DNA, or enzymatically, using proteins that cut it. Mechanical shearing produces more consistent fragment sizes, but enzymatic methods need less starting material and are simpler to execute. A third approach uses molecules called transposons that simultaneously cut the DNA and tag the fragments, combining multiple steps into one.
After fragmentation, the ragged ends of each fragment are repaired and small index sequences are added. These indexes act like barcodes, letting researchers mix dozens or even hundreds of different samples on a single flow cell and sort them out computationally afterward. This pooling strategy dramatically reduces the per-sample cost of sequencing.
The Hardware Lineup
Illumina sells sequencers at several scales, from small benchtop units for individual labs to production machines that can sequence tens of thousands of genomes per year.
- MiSeq i100 Series: A compact benchtop instrument producing up to 30 gigabases of data and 100 million reads per run. It’s suited for targeted gene panels, small genome sequencing, and microbiology applications where throughput needs are modest.
- NextSeq 1000/2000: A mid-range system generating up to 540 gigabases and 1.8 billion reads per run. It bridges the gap between small-lab flexibility and the throughput needed for whole exome sequencing or transcriptomics.
- NovaSeq X Series: The flagship production platform. A single flow cell produces 8 to 10.5 terabases of data and up to 35 billion reads. With dual flow cells running simultaneously, that doubles to 52 to 70 billion reads per run. This is the instrument powering large population genomics projects and high-volume clinical labs.
The jump in scale between these machines is enormous. A MiSeq run generates enough data to sequence a few bacterial genomes. A NovaSeq X run generates enough to sequence thousands of human genomes.
What Sequencing Costs Now
The cost of sequencing a human genome has fallen dramatically over the past two decades, and Illumina’s instruments have driven much of that decline. Academic pricing through sequencing service centers in 2025 lists a single lane of NovaSeq X Plus 10B sequencing (300 cycles) at roughly $1,823. A lane on the higher-capacity 25B flow cell runs about $3,040. A single whole human genome typically requires a fraction of one of these lanes, depending on the depth of coverage needed, putting the effective cost per genome well under $1,000 for many applications.
Software and Data Analysis
Sequencing an entire human genome produces hundreds of gigabytes of raw data. Turning that into medically or scientifically useful information requires serious computing power, and Illumina builds that into its ecosystem too.
The company’s DRAGEN platform uses specialized hardware (a custom processor chip) to dramatically speed up the computationally heavy work of aligning billions of short DNA reads against a reference genome, identifying variants, and flagging mutations. It runs analysis pipelines for whole genomes, exomes (just the protein-coding regions), RNA expression, DNA methylation patterns, and cancer genomics. For clinical labs processing hundreds or thousands of samples per week, this speed matters: analyses that once took hours on standard servers can finish in minutes.
Illumina also offers Connected Multiomics software, designed to pull together data from different types of molecular analysis (DNA, RNA, protein, and chemical modifications of DNA) into a single workflow. The goal is to let researchers look at multiple layers of biological information from the same sample without stitching together tools from different vendors.
Clinical and Medical Applications
Illumina’s technology sits behind several categories of clinical testing that have become routine in modern medicine.
Non-invasive prenatal testing, or NIPT, is one of the most widely recognized. A simple blood draw from a pregnant person, taken as early as 10 weeks of gestation, captures fragments of fetal DNA circulating in the mother’s bloodstream. Illumina’s NIPT platform sequences these fragments and screens for chromosomal conditions including Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13), with sensitivity and specificity above 99% for all three. It can also detect sex chromosome abnormalities and partial duplications or deletions across all chromosomes. The American College of Obstetricians and Gynecologists endorses NIPT as having the highest detection rate and lowest false positive rate of any prenatal screening option, regardless of maternal age.
In oncology, Illumina platforms power many of the genomic profiling tests that match cancer patients to targeted therapies. By sequencing tumor DNA, either from a tissue biopsy or from fragments shed into the bloodstream (liquid biopsy), clinicians can identify the specific mutations driving a patient’s cancer and select drugs designed to target them.
Agriculture and Environmental Science
Illumina’s reach extends well beyond human medicine. In agriculture, the same sequencing and genotyping technology helps breeders identify genetic markers linked to desirable traits in crops and livestock.
Syngenta, for example, uses Illumina sequencing to understand the genetic mechanisms behind drought tolerance in hybrid corn. Canadian dairy farmers have used genomic selection tools running on Illumina platforms for over a decade, with measurable gains in milk production and herd efficiency. Beef producers use Illumina’s genotyping arrays to verify parentage and select for quality traits in cattle. Veterinary scientists have used the MiSeq system to track the evolution and spread of emerging livestock viruses.
On the crop side, researchers use NovaSeq instruments to assemble the genomes of complex plant species from scratch, building the reference maps that make targeted breeding possible. These applications collectively fall under what the industry calls agrigenomics, and they represent a growing share of Illumina’s business outside clinical testing.
Expanding Into Proteomics
Illumina has historically been a DNA and RNA company, but it is pushing into protein analysis. The company acquired SomaLogic, a proteomics firm, to add protein measurement tools to its portfolio. The logic is straightforward: DNA tells you what a cell could theoretically make, but proteins tell you what it’s actually doing right now. Combining both types of data gives a more complete picture of health and disease.
Illumina now offers a protein preparation workflow and supports techniques like CITE-Seq, which captures protein and gene expression data from individual cells in a single sequencing run. The broader strategy is to become a one-stop platform for multiomics, integrating genomics, transcriptomics, epigenetics, and proteomics so researchers don’t need to cobble together systems from multiple vendors.