On 16 July 2015 the first experimental observations of Weyl fermion semimetal and topological Fermi arcs in an inversion symmetry-breaking single crystal material tantalum arsenide (TaAs) were made.[7] Both Weyl fermions and Fermi arc surface states were observed using direct electronic imaging using ARPES spectroscopy, which established its topological character for the first time.[7] This discovery was built upon previous theoretical predictions proposed in November 2014.[12][13]