In the first quarter of the twentieth century, physicists had come to believe that on the subatomic level, matter and energy were different aspects of the same phenomena. But there was no experimental support for this theory until 1927 when C.J. Davisson and his assistant, L.H. Germer, began investigating electron emission in vacuum tubes. Davisson directed a particle beam of electrons at a crystal of nickel and measured the pattern and energy of the electrons that returned. He found that the reflected electrons were not randomly scattered at lower energy, as would be the case with particles bouncing off the crystal, but returned with no loss of energy in a pattern that could only be described as a diffraction of waves. This discovery - that matter sometimes behaved as waves - helped to revolutionize thinking in theoretical physics and earned Davisson a Nobel Prize.