Psychometrics is a scientific discipline concerned with the construction of measurement models for psychological data. In these models, a theoretical construct (e.g., intelligence) is systematically coordinated with observables (e.g., IQ scores). This is often done through latent variable models, which represent the construct of interest as a latent variable that acts as the common determinant of a set of test scores. Important psychometric questions include (1) how much information about the latent variable is contained in the data (measurement precision), (2) whether the test scores indeed measure the intended construct (validity), and (3) to what extent the test scores function in the same way in different groups (measurement invariance). Recent developments have focused on extending the basic latent variable model for more complex research designs and on implementing psychometric models in freely available software.