Correlative Array Tomography

Correlative array tomography (CAT) makes use of the fixative agent glutaraldehyde and requires heavy metal staining for ultrastructural contrast. A key component of array tomography (AT) relies on the production of arrays of ultrathin sections from resin‐embedded biological samples. The need for correlative light and electron microscopy lies in the intrinsic properties of biological tissues, namely the intricate relationship between the molecular and physical architectures. Fixation, dehydration, and resin embedding are necessary steps in order to visualize biological tissue in electron microscopes. This chapter summarizes the key differences between CAT protocols for circuit tracing and for proteometric analysis. It briefly reviews several AT‐compatible techniques for the collection of ultrathin sections of resin‐embedded tissue. The chapter details imaging procedures for the two modalities: light microscopy and electron microscopy. Finally, it presents an application that demonstrates the power of CAT applied to the analysis of brain circuits.