 I am Francesco Longo, I am an astrophysicist. I am also associate professor in experimental physics at the University of Trieste. For the research activities I am associate to the Italian Institute of Nuclear Physics. Since the master degree I have been working on transient sources. For this reason I am currently the coordinator of a transient and multi-webland science group for the CTA consortium. Transient sources are celestial sources that vary the level of the intensity of their light emission in relatively short times. Observing varying phenomena is quite rare in our lights. So for example the explosion of massive stars called supernovae is quite rare phenomenon. Transient events are characterized by a large power. The energy that they emit is concentrated in a short amount of time. So being so powerful the transient event has a huge density of energy. So this huge density allows efficient particle acceleration processes. These sources can emit both electron and protons that then emit the very high energy emission that the CTA might reveal. CTA will reveal several examples of transient sources, several types of them. So we might find the explosion of stars at the origin of the universe. Mergers of neutron star events, these are the final stages of evolution of massive stars. Both these events emit a short powerful episode of gamma ray. These are called gamma ray bursts. These gamma ray bursts or G-armys are characterized by two phases. The first one, called prompt, lasts at maximum few minutes. The second one, called the afterglow, is a much longer emission, normally emitting photos in the X-rays down to the optical and the radio bands. This afterglow phase lasts up to days or even weeks. This discovery allowed the community to understand that these brief and intense flashes of gamma ray radiation were originated by sources located at the highest known distances. So the most distant source known so far is a gamma ray burst, originated when the universe had only 500 million years. Nowadays the universe has 13.7 billion years. So this source was originated when the universe was really heavy. Gamma ray bursts are then proving the very early universe. Other transient sources that CTA might reveal are associated with supermassive black holes. They reside at the center of galaxies differently from the Milky Way. In some cases a fraction of them show a very high activity in their center. They are called active galactic nuclei. These sources have an erratic behavior. They show transient events very often. I hope that for sure CTA will detect gamma ray bursts of long and short duration. They are associated to different progenitors. So far we know that long gamma ray bursts emit very high energy radiation, not yet the short one. So I hope that CTA will be able to get one thing. We have a reasonable hope to detect emission of very high energy in co-incident with gravitational wave events. In this case the capability of CTA to rapidly slew to the direction of a transient event is crucial because we can get the transient event detected in other wavelengths when still the source is active. It is also crucial the capability of the CTA that analyses to find transient sources in our own data. This is also the same amount of time, like 30 seconds. So CTA will be able to find if a transient source is present in the data stream in less than one minute. This will be communicated to the world and the location of this new very high energy transient can be pinpointed by other instruments. The daily life of a transient astrophysicist and astrophysicist working on transient sources like itself is quite challenging. I should say not only the daily life but also the likely life because whenever you are on shift as a burst advocate you shall be ready to react as soon as possible to a possible alert on a transient source. This fast reaction might result in a brief communication to all the telescopes that something has been observed by CTA and communicate its location and its first properties to other observers in other wavelengths that might decide to point to the same direction and get the source when it is still active. So the attention should be continuous, you shall be always ready to react to any kind of alert. The sky is so variable that transient activity is really, really challenging.