In a ground-up structural investigation of the cortex cells of human hair we have discovered that most hair macrofibrils have a structure different from any wool macrofibril. Modified wool staining methods in combination with high-resolution transmission electron microscopy, electron tomography and image analysis methods were used to better resolve the true nature of human hair cortex cells. All observed macrofibrils were made up of intermediate filaments (IFs) that were arranged helically around the macrofibril long axis. Being helical, IFs had no radial tilt but did have tangential tilt. IFs close to the centre of macrofibrils had lower tangential tilt compared to those close to the macrofibril periphery. This architecture is familiar from the wool orthocortex, but also differs from wool because both the range of IF tangential tilts within macrofibrils and macrofibril size vary considerably within and between cells, and taken across the extent of the cortex these cell-type variations correlate with differences in gross hair morphology (straight vs. high-curl). We introduce new terminology to objectively describe the structure of human hair cortex and present a hypothesis to explain the variation in structure observed between macrofibrils that has implications for all hard-keratin fibres.