Performing experiments that involve a large amount of resources or a complex configuration proves to be a hard task. In this paper we present Expo, which is a tool for conducting experiments on distributed platforms. First, the tool is described along with the concepts of resource and task sets, which abstracts away some of the complexity in the experiment conduction. Next, the tool is compared with other similar solutions based on some qualitative criteria, scalability and expressiveness tests, as well as the feedback coming from using dedicated testbeds. The paper finishes with the evaluation of Expo scalability and some use cases on Grid5000 and PlanetLab testbeds. Our experience showed that Expo is a promising tool to help the user with two primary concerns: performing a large scale experiment efficiently and easily, together with its reproducilibity.