Microglial cells, as their name implies, are the smallest type of glial cells. Under a microscope, their small and elongated nuclei have a dash-like form, making them easily distinguishable from the larger and rounded nuclei of other cell types.

Here, we assess the current knowledge of the diverse microglial morphologies, with a focus on the correlation between microglial shape and function.

In particular, the microglial cell density, cell shape, distribution pattern, distinct microglial phenotypes and interactions with other cell types should be evaluated.

These findings suggest that microglial morphological plasticity not only contributes to physiological functions, but it is also intimately involved in neuropathological contexts.

We highlight some of the specific microglial morphological features that we consider important for their functional spectrum and future classifications.

In a healthy state, microglia display a ramified morphology, characterized by a small cell body and numerous long, thin, highly branched processes. These processes are highly mobile, allowing the cell to survey large volumes of brain tissue.

Pericapillar microglial cell in 3D.

Microglia have cell processes or projections which have an appearance of a thorny bush. The nuclei of microglia are small, dense, and elongated which distinguishes them from other glial cells which exhibit spherical nuclei.

Through rigorous investigation of microglial morphology in models of health and disease, we aim to appreciate the consequential, and often nuanced, role of these cells in the development and persistence of neuropsychiatric disease.

Although microglial cells are dark like oligodendrocytes, they usually have bean shaped nuclei and the contours of their cell bodies are more irregular than those of oligodendrocytes.