Background

The EEG was first developed in 1929 by Hans Berger, who also discovered the Alpha wave, a brain wave that becomes prominent in times of rest and relaxation. At the time, brain waves were little understood and would remain mysterious and difficult to analyze for many years. The EEG started to come back to significance with the advent of the fast Fourier transform in the mid 20th century. With the ability for researchers to properly analyze the different frequencies in the brain, more in depth studies were now more possible and a whole slew of discoveries were made near the end of the 20th century.

Left: Hans Berger's EEG device

https://www.neuroelectrics.com/blog/hans-berger-lights-and-shadows-of-the-inventor-of-electroencephalography/

As for the present day, EEG's have now become a centerpiece in human research and currently are part of a large and growing market of both research grade devices like the X24 from Advanced Brain Monitoring and home use experimental devices like the relatively low cost OpenBCI Ganglion Board. Applications for EEG's today range from diagnosing mental disorders, sleep disorders, and other ailments to being used as controllers for mobility devices, similar to the one being pictured on the right. Combinations of systems that integrate EEG recorders with live convolutional neural nets allow a user to control mechanical objects with no physical inputs. While for research, wet EEG devices like the one pictured to the right are still the golden standard for accuracy and precision, home use devices are becoming more and more common.

Right: Wet EEG device with inputs controlling the movement on a wheelchair

https://www.technologyreview.com/s/420756/wheelchair-makes-the-most-of-brain-control/