This paper describes the preparation and understanding of helical peanut-shaped ribbons of poly(vinyl pyrrolidone) (PVP) by a magnetic field-assisted electrospinning method. The relative humidity is found to significantly influence the morphology of PVP fibers. The morphology changed from straight rods to helical ribbons as relative humidity decreased. The percentage of helical ribbons increased dramatically as well. At the same time, the cross-section of electrospun fibers changed from circle, to ellipse, and to peanut shape. Formation of helical ribbons is attributed to the synergistic interaction of bending instability and rigidity of the polymers during the electrospinning process. These fibers had different mechanical properties and the helical ribbons were shown to have the largest ultimate elongation. (C) 2013 Elsevier Ltd. All rights reserved.