In complex projects, it is common to perform multi-step sequences of calculations which use the structure of a previous calculation as input. This is typically called a computational workflow. Furthermore, branching can occur in these processes, thus forming a complex tree of linked calculations. This can be confusing and lead to errors and time loss. To address this issue, CalcUS keeps track of the origin of each ensemble and constructs a visual, interactive ensemble tree for each molecule (Figure ). The user can provide custom names to ensembles for clarity. Clicking on any node redirects the user to the corresponding ensemble page. One advantage of using a relational database like PostgreSQL is the ability to link objects together in a non-linear fashion. For example, this is what allows the creation of ensemble trees, such as the one illustrated in Figure . Moreover, the ensemble properties (e.g. Boltzmann-weighted energies) can be calculated dynamically by querying all the structures belonging to that ensemble and performing the appropriate weighting. These relationships do not need to follow a restrictive top-down organization, such as in folders and subfolders. As such, data can be organized simultaneously in different ways and efficiently retrieved in multiple ways.