A catalyst particle for use in growth of elongated nanostructures, such as e.g. nanowires, is provided. The catalyst particle comprises a catalyst compound for catalyzing growth of an elongated nanostructure comprising a nanostructure material without substantially dissolving in the nanostructure material and at least one dopant element for doping the elongated nanostructure during growth by substantially completely dissolving in the nanostructure material. A method for forming an elongated nanostructure, e.g. nanowire, on a substrate using the catalyst particle is also provided. The method allows controlling dopant concentration in the elongated nanostructures, e.g. nanowires, and allows elongated nanostructures with a low dopant concentration of lower than 1017 atoms/cm3 to be obtained.