We all physicist have long been believed that an elementary particle is a wave as well as a particle, but we discuss in this paper that an electron (probably all fermions) is always a particle. Author claim that quantum mechanics (QM) is not such mysterious as Bohr stated that the wave turn to the particle by observation. We can understand QM by natural human sense. The wave nature of electrons is only an appearance or a phenomena but not intrinsic or substantial. An electron is an individual body, which interferes with other individual electrons. Interference is the key word instead of the wave to understand the quantum mechanics. Interference produces the wave nature and the uncertainty. When we determine that an electron is nothing but a particle, we will see the true meaning of wave function and the Schr?dinger’s equation.
 A. Einstein, B. Podolsk and N. Rosen, “Can Quantum- Mechanical Description of Physical Reality Be Considered Complete?” Physical Review, Vol. 47, No. 10, 1935, pp. 777-780. doi:10.1103/PhysRev.47.777
 A. Aspect, J. Dalibard & G. Roger, “Experimental Test of Bell’s Inequalities Using Time-Varying Analyzers,” Physical Review Letters, Vol. 49, No. 25, 1982, pp. 1804-1807. doi:10.1103/PhysRevLett.49.1804
 J. Erhart, S. Sponar, G. Sulyok, G. Badurek, M. Ozawa and Y. Hasegawa, “Experimental Demonstration of a Universally Valid Error—Disturbance Uncertainty Relation in Spin Measurements,” Nature Physics, Vol. 8, 2012, pp. 185-189.
 Heisenberg, “Uncertainty Principle.” http://en.wikipedia.org/wiki/Uncertainty_principle
 Pauli Principle. http://en.wikipedia.org/wiki/Pauli_exclusion_principle