From 1905 Nienhuis lecturer at the School of Applied Arts in Haarlem. He began that year with jewelry design for the jewelry firm Hoeker &amp; Son. For one of his designs he was awarded a silver medal at the 1910 World Fair in Brussels. In his early jewelry design, until 1912, Nienhuis used simple abstracted natural ornaments in both the decoration and in the shape. He especially worked with gold, precious stones and enamel work. His ornaments are considered examples of the Dutch art nouveau.