The term "adaptive optics" conjures images of complicated and expensive systems. Researchers at Delft University of Technology in the Netherlands hope to change that. In the May 1 issue of Optics Letters, they describe a deformable mirror driven with resistors that cost them less than $100 to build.The new system, which may find use in scientific and medical applications that do not require fast response times, features 19 off-the-shelf metal-film resistors glued to the back of the 5-cm mirrored silicon wafer. A 20-channel, 8-bit digital-to-analog converter controlled the current to the resistors and, thus, their length. The system displayed a 5-s response time and suffered thermal tremors, but it offered a temporal stability of approximately λ/10 at 633 nm.