English: Jets in the early Universe give astronomers a way to probe the growth of black holes at a very early epoch in the cosmos. Using Chandra, astronomers recently discovered a jet in X-rays being illuminated by the cosmic microwave background. The light from this jet was emitted when the Universe was only one fifth of its present age. The main panel of this graphic shows Chandra's X-ray data combined with an optical image, while the inset focuses on the details of the X-ray emission.