In 1977, Frederick Sanger developed a method to read DNA. It was slow and laborious, but it worked. The first human genome took 13 years and cost $2.7 billion. Today, a human genome can be sequenced in a day for under $1,000. The technology has transformed biology, medicine, and our understanding of life.

Sequencing determines the order of nucleotides in a DNA molecule. Early methods, like Sanger sequencing, used chain-terminating nucleotides and gel electrophoresis. Next-generation sequencing, introduced in 2005, parallelizes the process. Millions of DNA fragments are sequenced simultaneously, generating massive amounts of data. Third-generation platforms, like those from Oxford Nanopore and PacBio, read longer fragments and can detect modifications.

Sequencing is used everywhere. It diagnoses genetic diseases and guides cancer treatment. It tracks outbreaks of infectious diseases. It identifies species and reconstructs evolutionary relationships. It monitors ecosystems by sequencing environmental DNA. It is a foundational technology.

The challenge is no longer generating data. It is interpreting it. A human genome contains millions of variants, and most are harmless. Distinguishing the ones that matter requires databases, algorithms, and clinical judgment. Sequencing is easy. Understanding is hard.