The understanding and measurement of the brain is accomplished by various means. EEG (Electroencephalogram), Computerized Axial tomography, Positron Emission tomography, Magnetic resonance imaging and Magnetoencephalography. EEG was among the first measurements undertaken to understand the working of the brain. It is a summation of the electrical activity of the brain. The audio analogy to understanding its signal is to turn on ~100 FM radio channel’s at the same time and then try to understand the current news channel. The interference is tremendous and researchers have used a variety of methods to understand their meaning. One way that is most common is to break up the complex wave signal into separate components or frequencies and try to understand their meaning. The signal that is captured is also dependent on the number of electrodes. The simplest possible is two electrodes and that is commercialized by Neurosky, and the highest number of electrodes is in the hundreds. The signal that is measured is in micro-volts so is obviously very sensitive to any muscle movement or numerous other factors including the precise placement of the electrodes. There has been tremendous amount of work that that has been done to classify the waves into distinct patterns and also map different regions of the brain. The discussion of classification of different frequencies is shown with their generalized function in the image but this is a large summation of the frequencies that are observed near the cortex of the brain. It is expected the frequency would be dependent on the location where the measurement was done and the proximity of the neuron. EEG is very accurate to determine the activity of the brain during patient brain death or other calamitous occasions. It has also been shown that the activity being performed can change the frequency of the brain. It has been proposed that locked-in patients will be able to communicate using some form of brain frequency manipulation.