Variability is omnipresent in numerous kinds of artefacts (e.g., source code, product matrices) and in different shapes (e.g., conditional compilation, differences among product descriptions). For understanding, reasoning about, maintaining or evolving variability, practitioners usually need an explicit encoding of variability (ie a variability model). As a result, numerous techniques have been developed to reverse engineer variability (e.g., through the mining of features and constraints from source code) or for migrating a set of products as a variability system. In this talk we will first present tool-supported techniques for synthesizing variability models from constraints or product descriptions. Practitioners can build Boolean feature models with an interactive environment for selecting a meaningful and sound hierarchy. Attributes can also be synthesized for encoding numerical values and constraints among them. We will present key results we obtain through experiments with the SPLOT repository and product comparison matrices coming from Wikipedia and BestBuy. Finally we will introduce OpenCompare.org a recent initiative for editing, reasoning, and mining product comparison matrices. This talk has been done at REVE'15 workshop co-located with SPLC'15 (software product line conference): http://www.isse.jku.at/reve2015/program.html