“I know me” is an interactive artwork that produces images based on EEG measurements from human participants. Although artists have previously made some interactive image works, we considered using human physiological information as input because it reflects human feelings better. In this research we were interested in information about human's mental states, such as anger or sadness. Brain activity was observed with EEG, subjected to Fourier analysis and converted into an animation based on a Lissajous curve. We generated images corresponding to alpha or beta waves activity in real time and showed them to the observer. The observer understood his own mental condition from looking at the images, and could potentially control his own mental state with this interactive device.