Multielectrode arrays are an essential tool in experimental and clinical neuroscience, yet current designs are severely limited by a mismatch between large or stiff electrodes and the fragile environment of the brain. Chronically implanted electrodes cause ongoing damage to the brain, and an active process of rejection eventually silences neural signals. A self-splaying microelectrode array is proposed for recording and control of brain activity. The array comprises a bundle of carbon micro threads, each insulated except for an exposed, sharpened electrode tip. The threads are extremely fine with diameters as small as 4 μm in the devices used to obtain preliminary data. The bundle of microthreads is held together in a monolithic structure by van der Waals forces and is stiff enough to handle and implant without buckling. As the array enters the tissue, the individual microthread electrodes splay in a pattern determined by the local micromechanical environment of the tissue. Each microthread follows a unique, one-dimensional path that prevents tissue damage as the bundle splays. For each electrode site, the microthread displaces less than 2 % of the tissue displaced by a conventional microelectrode and exposes the brain to less 10 % of the non-biological surface area of a conventional microelectrode. We hypothesize that future devices built on this self-splaying electrode principle will achieve unprecedented channel count and sampling density while maintaining reduced tissue responses and greatly improved chronic neural recording. Chronic recording data in songbirds supports this hypothesis.