DNA array to protein array (DAPA) is a method developed in 2007 to repeatedly produce protein arrays by ‘printing’ them from a single DNA template array, on demand (Figure 5). It starts with the spotting and immobilization of an array of DNA templates onto a glass slide. The slide is then assembled face-to-face with a second slide pre-coated with a protein-capturing reagent, and a membrane soaked with cell extract is placed between the two slides for transcription and translation to take place. The newly synthesized his-tagged proteins are then immobilized onto the slide to form the array. In the publication in 18 of 20 replications a protein microarray copy could be generated. Potentially the process can be repeated as often as needed, as long as the DNA is unharmed by DNAses, degradation or mechanical abrasion.