Tunneling nanotubes (TNTs) are thin tubular membrane protrusions that connect distant cells, generating a complex cellular network. Over the past few decades, research on TNTs has provided important insights into their biology, including structural composition, formation mechanisms, modulators, and functionality. It has been discovered that TNTs allow cytoplasmic continuity between connected cells, facilitating fast intercellular communication via both passive or active exchange of materials. These features are pivotal in the nervous system, where rapid processing of inputs is physiologically required. TNTs have been implicated in the progression of neurodegenerative diseases and cancer in various