
A grid of hundreds of micro-scale electrodes used to record electrical activity from many neurons simultaneously.A microelectrode array (MEA) is a device consisting of hundreds or thousands of microscopic electrodes arranged in a grid, designed to record or stimulate electrical activity from neurons, cardiac cells, or other excitable tissues. Unlike a single electrode, which captures the activity of one neuron, an MEA captures the simultaneous firing patterns of many cells, revealing how networks process information. MEAs are used both in vitro (on cultured cells) and in vivo (implanted in living brains), and they have become a cornerstone of modern neuroscience and bioengineering.
The first planar microelectrode arrays were developed in the early 1970s by C.A. Thomas and colleagues, building on earlier work with single microelectrodes. The technology matured through the 1990s with the advent of CMOS fabrication, allowing thousands of electrodes on a single chip.
Each electrode in the array is a tiny conductive contact, typically made of gold, platinum, or indium tin oxide, with a diameter of 10–30 micrometers. When a neuron fires, it produces a local voltage change that the electrode picks up; the signal is then amplified, digitized, and recorded. The spacing between electrodes is chosen to match the density of the cells under study — close enough to capture individual neurons, but far enough to avoid excessive crosstalk. Advanced MEAs can also stimulate cells by passing current through selected electrodes, enabling closed-loop experiments where activity is both read and written.
MEAs are used in drug screening for cardiac toxicity, in brain-machine interfaces for prosthetic control, and in basic research on learning, memory, and neural network dynamics.
Modern high-density MEAs can record from more than 20,000 neurons simultaneously — a number that exceeds the total number of neurons in the brain of a fruit fly.











