Transmission electron microscopy (TEM) is widely used as an imaging modality to provide high-resolution details of subcellular components within cells and tissues. Mitochondria and endoplasmic reticulum (ER) are organelles of particular interest to those investigating metabolic disorders. A straightforward method for quantifying and characterizing particular aspects of these organelles would be a useful tool. In this protocol, we outline how to accurately assess the morphology of these important subcellular structures using open source software ImageJ, originally developed by the National Institutes of Health (NIH). Specifically, we detail how to obtain mitochondrial length, width, area, and circularity, in addition to assessing cristae morphology and measuring mito/endoplasmic reticulum (ER) interactions. These procedures provide useful tools for quantifying and characterizing key features of sub-cellular morphology, leading to accurate and reproducible measurements and visualizations of mitochondria and ER.

High-resolution 3D images of organelles are of paramount importance in cellular biology. Although light microscopy and transmission electron microscopy (TEM) have provided the standard for imaging cellular structures, they cannot provide 3D images. However, recent technological advances such as serial block-face scanning electron microscopy (SBF-SEM) and focused ion beam scanning electron microscopy (FIB-SEM) provide the tools to create 3D images for the ultrastructural analysis of organelles. Here, we describe a standardized protocol using the visualization software, Amira, to quantify organelle morphologies in 3D, thereby providing accurate and reproducible measurements of these cellular substructures. We demonstrate applications of SBF-SEM and Amira to quantify mitochondria and endoplasmic reticulum (ER) structures.

Mentoring is a developmental experience intended to increase the willingness to learn and establish credibility while building positive relationships through networking. In this commentary, we focus on intentional mentoring for underrepresented mentees, including individuals that belong to minority racial, ethnic, and gender identity groups in Science, Technology, Engineering, Mathematics, and Medicine (STEMM) fields. Intentional mentoring is the superpower action necessary for developing harmony and comprehending the purpose and value of the mentor/mentee relationship. Regardless of a mentor's career stage, we believe the strategies discussed may be used to create a supportive and constructive mentorship environment; thereby improving the retention rates of underrepresented mentees within the scientific community.

Mitochondrial dynamics and morphology (fission, fusion, and the formation of nanotunnels) are very sensitive to the cellular environment and may be adversely affected by oxidative stress, changes in calcium levels, and hypoxia. Investigating the precise relationship between the organelle structure and function requires methods that can adequately preserve the structure while providing accurate, quantitative measurements of mitochondrial morphological attributes. Here, we demonstrate a practical approach for preserving and measuring fine structural changes in two-dimensional electron micrographs, obtained using transmission electron microscopy, highlighting the specific advantages of this technique. Additionally, this study defines a set of quantifiable metrics that can be applied to measure mitochondrial architecture and other organellar structures. Finally, we validated specimen preparation methods that avoid the introduction of morphological artifacts in mitochondrial appearance that do not require whole-animal perfusion.

Various intracellular degradation organelles, including autophagosomes, lysosomes, and endosomes, work in tandem to perform autophagy, which is crucial for cellular homeostasis. Altered autophagy contributes to the pathophysiology of various diseases, including cancers and metabolic diseases. This paper aims to describe an approach to reproducibly identify and distinguish subcellular structures involved in macroautophagy. Methods are provided that help avoid common pitfalls. How to distinguish between lysosomes, lipid droplets, autolysosomes, autophagosomes, and inclusion bodies are also discussed. These methods use transmission electron microscopy (TEM), which is able to generate nanometer‐scale micrographs of cellular degradation components in a fixed sample. Serial block face‐scanning electron microscopy is also used to visualize the 3D morphology of degradation machinery using the Amira software. In addition to TEM and 3D reconstruction, other imaging techniques are discussed, such as immunofluorescence and immunogold labeling, which can be used to classify cellular organelles, reliably and accurately. Results show how these methods may be used to accurately quantify cellular degradation machinery under various conditions, such as treatment with the endoplasmic reticulum stressor thapsigargin or ablation of the dynamin‐related protein 1.