NeuronViewerVR is the first app for viewing neurons in the descriptive .swc file format on demand in mixed reality (MR). Neurons in the .swc format from arbitrary sources can be manually uploaded to the headset and placed in an MR space. While MR enables the fast display of the neurons and allows the user to walk around them without setting up a proper play space, the app also supports dynamic blending between a transparent and black background for better contrast. Furthermore, a direct interface for accessing all neurons in the Neuromorpho (www.neuromorpho.org) database, which contains ~200,000 neurons from numerous different species traced by various scientists, was implemented. Neurons can be placed in different colors, favorites can be added from Neuromorpho and even whole forests of neurons manually uploaded to the headset or downloaded from Neuromorpho can be saved and loaded at later timepoints.