Cloud Computing, a technology that uses the internet and central remote servers to maintain data and applications. Cloud computing permits consumers and businesses to use applications without installation and access their personal files at any computer with internet access. This technology permits for much more efficient computing by centralizing storage, memory, processing and bandwidth. The focuses will be on the emerging field of Cloud computing and especially on the middle layer called PaaS . It aims to understand the layer PaaS and implement it, exploiting features such as scalability and accessibility to name a few.