1995 Researchers at Stanford University, led by Pat Brown and Ron Davis, work out a recipe for making DNA chips right in the laboratory. Instead of building the probes one nucleotide at a time on a silicon surface, à la Affymetrix, these researchers spot whole DNA fragments onto a glass microscope slide. To make their arrays, Brown and his colleagues build a robot that uses fountain pen-like tips to dot tiny droplets of a solution containing the DNA probes-large pieces of genes copied by PCR-onto the slide. These DNA chips are like the dot blots developed in the '70s, only better: They're more sensitive, they require less sample DNA, they don't rely on radioactivity, and you can do tens of thousands of blots in a single run. Once a lab is geared for production, Brown estimates, chips will cost about $20 apiece. His Stanford Web site offers complete instructions for any lab interested in do-it-yourself DNA chips, making the technology accessible to the scientific community.