The analysis of ferromagnetic nanowires is a new and vivid field of research. Micromagnetic simulations based on the finite-element method are being used to gain an insight into the dynamics of the reversal process of such wires. Two different types of reversal modes occur, depending on the wire thickness. While in thin wires a simple domain wall nucleates and propagates along the wire axis, the reversal of thick wires is achieved via a localized curling mode. The latter mode involves the injection and propagation of a micromagnetic singularity (Bloch point). The transition between the different modes is observed in a cone-shaped wire with linearly varying thickness.