It has been proposed that cellular calcium signalling is coordinated through an intracellular network of cytoplasmic nanocourses, namely the cell-wide web, demarcated by sarco/endoplasmic reticulum (S/ER) nanojunctions that span from outer nuclear membrane to the plasma membrane¹. At the centre of the cell-wide web are cytoplasmic nanocourses demarcated by nuclear envelope invaginations (NEIs). Although their function remains open to question, evidence indicates that the nuclear envelope lumen holds a calcium store that is released into cytoplasmic nanocourses demarcated by NEIs rather than into the nucleoplasm, and that modulating calcium flux across the outer nuclear membrane correlates with changes in gene expression in pulmonary arterial myocytes¹.  Nuclear invaginations are evolutionarily conserved and are found in other mammalian cells², including neurons³. Our aim was, therefore, to determine whether the cell-wide web coordinates calcium signalling in primary mouse cortical neurons isolated from mouse embryos (E17.5) after 7 days of culture. Fixed neurons were labelled by ER‑kit (Abcam), Lamin A and Lamin B1 antibodies following immunolabelling methods adapted from those used previously¹. 3D reconstruction of deconvolved confocal images strongly suggested that both NEIs and the cell‑wide web were present in primary mouse cortical neurons. There were ~55 (given mean ± SEM) NEIs per cell, of which 32.4 ± 3.0 (n = 5) were both lamin A and lamin B1 positive, 21.8 ± 4.9 (n = 5) were lamin A positive and lamin B1 negative, and 1.8 ± 0.7 (n = 5) were lamin B positive and lamin A negative. Lamin B positive NEIs were found to co-localise with the histone mark H3K9me2, consistent with their proposed role in gene expression regulation¹. Live‑cell confocal imaging was then carried out on cortical neurons loaded with the calcium indicator Fluo‑4 (Life Technologies), ER-tracker (Thermo Fisher) and Draq5 (Thermo Fisher). This revealed a cell-wide web of Fluo-4 positive cytoplasmic nanocourses that colocalised with ER-Tracker. Within different cytoplasmic nanocourses asynchronous calcium signals were observed in the absence of applied stimuli. More strikingly still, pre‑incubation (1 min) of Bicuculine (50 mM) and 4-Aminopyridine (250 mM), which have been shown to induce action potential firing by synaptic release of glutamate⁴, evoked calcium transients in primary cortical neurons that arose at dendrites (Fmax/F0 = 2.20 ± 0.15, n = 5) and propagated through cytoplasmic nanocourse into the soma and NEIs (Fmax/F0= 2.46 ± 0.19, n = 5) but not the nucleoplasm, and finally through the axon. Notably the calcium signal within cytoplasmic nanocourse demarcated by NEIs declined more slowly (time to 50% of max = 4.27s ± 0.61s, n = 5) than in extraperinuclear nancourses across the wider cell (time to 50% of max = 2.53s ±  0.40s, n = 5). We conclude that in cortical neurons calcium signalling is coordinated through the cell‑wide web at NEIs and beyond.