Brain Computer Interfacing (BCI) aims at making use of brain signals for e.g. the control of objects, spelling, gaming and so on. This tutorial will first provide a brief overview of the current BCI research activities and provide details in recent developments on both invasive and non-invasive BCI systems. In a second part -- taking a physiologist point of view -- the necessary neurological/neurophysical background is provided and medical applications are discussed. The third part -- now from a machine learning and signal processing perspective -- shows the wealth, the complexity and the difficulties of the data available, a truely enormous challenge. In real-time a multi-variate very noise contaminated data stream is to be processed and classified. Main emphasis of this part of the tutorial is placed on feature extraction/selection and preprocessing which includes among other techniques CSP and also ICA methods. Finally, I report in more detail about the Berlin Brain Computer (BBCI) Interface that is based on EEG signals and take the audience all the way from the measured signal, the preprocessing and filtering, the classification to the respective application. BCI communication is discussed in a clincial setting and for gaming.