DEPFET active pixel detectors. The concept of the Depleted Field Effect Transistor (DEPFET) was proposed by Lutz and Kemmer in the 1980s. A group of institutes is now developing the DEPFET as the building block for an active pixel detector to be applied in future collider experiments. The "active" in "active pixel detector" stands for the integration in the sensor of some of the functionality traditionally reserved for the Front End read-out electronics. In the case of a DEPFET the Field Effect Transistor integrated in each pixel on a high resistivity silicon wafer takes care of a first amplification of the signal. Thus, a finely segmented pixel detector can be read out with low noise and very low power consumption. More information on the DEPFET concept can be found on these web pages . Just for insiders: the puzzle of the month is found here.