Majorana fermions are particles identical to their own antiparticles, first introduced by Majorana as hypothetical elementary particles. Subsequently they were predicted in topological superconductors as quasiparticles of zero energy and zero charge. We have implemented a recipe for Majoranas that has four simple ingredients: 1) one-dimensional wires 2) spin-orbit interaction 3) superconductivity and 4) magnetic field. I will present electrical measurements on nanowires grown from indium antimonide, a material with strong spin-orbit interaction. Nanowires are contacted by a superconducting electrode. In the presence of magnetic field of order 100 mT we observe bound states at zero bias voltage. These bound states remain fixed to zero bias even when magnetic field and gate voltages are changed over considerable ranges. At the same time, such robust peaks are not observed when we remove magnetic field, align it with spin-orbit field or replace a superconductor with a normal metal. Our observations support the hypothesis of Majorana fermions.