Molecular quantitative trait locus (molQTL) mapping associates genetic variation with molecular traits that can be measured as gene expression, splicing and chromatin accessibility. In this Primer, Aguet et al. discuss the study design and implementation of molQTL mapping in various applications, with a focus on technical developments for functional characterization.

Covalent organic frameworks (COFs) are a class of crystalline porous polymers consisting of highly ordered organic structures formed by polymerization. In this Primer, Tan et al. discuss the design principle, experimental methods, characterization and applications of COFs.

Principal component analysis is a multivariate statistical method that reduces a large number of variables into fewer variables, called principal components. This Primer describes how the method can be used for data analysis, explaining the mathematical background, analytical workflows, how to interpret a biplot and variants of the method.

Hydrogels are used to mimic cells’ local environment, enabling the study of cellular responses to biochemical and mechanical cues. Here, Blache et al. discuss the challenges of creating hydrogels for mechanobiology studies and how they can be used to analyse cell behaviour in the context of mechanobiological processes and harnessed to create regenerative therapies.

Tandem mass spectrometry is increasingly utilized for clinical applications in laboratory medicine. In this Primer, Thomas et al. discuss experimental considerations and quality management for implementing clinical tandem mass spectrometry in the clinic with an overview of some key applications.

Organoids are cell-based in vitro models derived from stem cells, reconstituting the complex structure and function of the corresponding tissue. In this Primer, Zhao, Chen, Dowbaj, Sljukic, Bratlie, Lin et al. discuss the development of organoids and methods for controlling their cellular environment.