 Since the beginning of time, humans have wondered about what the universe is made of and wanted to investigate and understand it. Today, we still only know about 4% of the cosmos, and almost everything we have learned so far, we have learned through electromagnetic radiation, through light. The particles and gamma rays are given enormous energies by cosmic particle accelerators. The former flight with the highest energy is called gamma rays. Gamma rays come to us straight from high energy processes in exploding stars or ultra-compact objects like neutron stars or black holes. Gamma rays are unable to pass through the Earth's atmosphere, but scientists are still able to detect them by taking advantage of a unique technique. They use telescopes to observe the cascades of secondary particles, which are produced when gamma rays hit the atmosphere. The cascade particles create the so-called Turenkov light. From the cascade's energy and direction, the scientists can then find the source of the gamma rays. About a hundred years ago, Viktor Hess discovered cosmic radiation with his balloon experiments. The mystery of their sources has not yet been solved completely. In the 1930s, Pavel Turenkov discovered the effect which is now used to observe atmospheric showers. But astronomy with gamma rays was first achieved by Trevor Weeks and his group. The people started in the sky for 30 years and there were many theorists, many physicists, who explained it crazily. One said that there can't be any stars, that there are objects that emit light with these very, very high energies. And they proved the opposite. All the ingredients needed to detect these extremely short bursts of Turenkov light generated by particle cascades in the atmosphere were already available in 1948. Twenty years later, Trevor Weeks built the Whipple Telescope. But it took until 1989 for him to detect the first source of gamma rays in the Krapnebula. The method was proven. Hegra was the start of the European efforts for detecting cascades with multiple telescopes, which were also continually improved in sensitivity. After Hess was commissioned initially with four telescopes, scientists were also able to show that some gamma ray sources are extended and cover the size of the full moon. Today, astro-particle physicists can study over 150 sources. Many of these had never been seen before in other wave bands, and some sources are still unidentified. Hess and its sister experiments Veritas and Magic were able to improve the methods for detecting gamma rays with Turenkov light. This technology is now well understood. Around 100 telescopes of different sizes will view the entire sky. The plan is to build around 20 telescopes in the northern hemisphere and 70 to 100 telescopes on around 10 square kilometres in the southern hemisphere. There are many challenges. The main one, I think, is just the sheer scale of the undertaking. So if we build something like 100 telescopes, we should make sure they're extremely efficient and reliable detectors, as well as working hard to make sure that we get the best value for money, essentially. For me, this is the main challenge, to make the whole thing realizable on the time scale we want and to make it reliable. The CTA team consists of 1,100 experts from 28 countries, a truly global consortium. The largest individual group in this international project is from Daisy. The German federal government supports CTA as one of the most important scientific projects of the coming years. Daisy is responsible for the design and construction of the medium-sized telescopes with a mirror of 12 metres diameter and has a leading role in the development of the telescope control. The logistical challenge is huge. New telescopes have to be designed and optimised, considering simultaneously scientific, economic and mass production aspects. Daisy is responsible for producing the right scientific output. Especially for Daisy, at the site of Zeuten, which is a centre for astroteiches, including gamma astronomy, the future project for us is very important. What we want to do scientifically in the next 10 to 20 years depends on the CTA. Daisy is able to rely on its in-house teams of engineers and technicians to support the scientists. The medium-sized telescope is a completely new design and nothing is left to chance. Feasibility studies go hand in hand with continuous evaluation and testing of components. The main emphasis is on the electric motors which are needed to drive the huge telescopes quickly and accurately and the mirrors needed to capture the faint flashes of Trenkov light. This expertise is applied to the development of the whole array. Scientists calculate all possible configurations of the telescopes to find the optimal one for reliably detecting the gamma-ray sources and recording precisely their energy and arrival direction. To learn all about the production processes and the materials involved in the project and to reduce the costs of producing the final array To learn all about the production processes and the materials involved in the project and to reduce the costs of producing the final array, Daisy has built a prototype for the medium-sized telescope. The engineers worked with local steel-building contractors to find out if special equipment is needed for the project The engineers worked with local steel-building contractors to find out if specialist companies are needed or if the telescopes can be constructed quickly, dependably and with a required precision by combining Daisy expertise with local know-how. The answer is yes they can, even better than expected. Now we measure a lot of sources because this is a golden age of astronomy. Everything we have learned in the time of Hess and Magic and Veritas can now be implemented in the CTA. Typically, it is so that there is no gap in our territory because of the lack of knowledge. Now we have all the people on board who have the experience to build things but also to operate things and to do physics. This is the next logical step. You cannot measure it for ten more years and you have to make a new step. This is the CTA. 2013 saw the construction of a one-of-a-kind version of the medium-sized telescope in Berlin, Atlas Hof. Around 40 telescopes of this type will be built for CTA. The prototype has remarkable dimensions. It is 35 metres high and consists of 75 tonnes of steel. The distance from the camera to the centre of the mirror is 16 metres and the camera weighs about 2 tonnes. Obviously, forces on the support elements are huge. The dish has a diameter of about 12 metres. The 100 square metres of mirror act like a sail or a parachute in the wind. Still, the telescope is designed to keep pointing in the right direction in winds gusting up to 35 kilometres per hour. The telescope was built to be powerful yet precise. It needs the precision to be able to track a source across the sky or to slew to the position of a gamma ray burst in less than 90 seconds. The mirrors are supplied by institutes in Poland, Italy and France. They too have to survive the field test. They are especially sensitive to environmental conditions. Changes in temperature, blowing sand and moisture will reduce their efficiency and thus influence the lifetime of the whole telescopes. The prototype meets all the expectations. With a working camera, it could actually be used for gamma ray observations if it was located in a dark, clear desert region and not in Berlin. Daisy has done its homework. But what will the complete array with 70 to 100 telescopes be capable of? I personally would like to see that matter with CTA. That if we see that matter with CTA, that would be probably the most important discovery in this century. Gamma rays are actually a unique message. That's the most exciting thing. That's generally the most exciting thing about astronomy. Whenever you turn on a new telescope, you see things you didn't expect. We think we give ourselves the best chance to discover the unexpected effectively. So whilst we have an eye on all these sort of known questions, we don't know the answers, but in some cases we know the questions. One of the most exciting things about the array is expanding our knowledge of the universe over a very wide energy range. We think there's real potential to discover the completely new.