eng Science and Education Publishing International Journal of Physics 2333-4576 2020-11-09 8 4 153 157 10.12691/ijp-8-4-6 IJP2020846 article Hui Peng davidpeng1749@gmail.com Young¡¯s one-dimension-double-slit experiment represents the basic mystery of quantum world and was extended to which-way-1D-double-slit experiment. To explore the mystery, 2D-cross-double-slit apparatuses have been proposed, which consists of more than one double-slits intersecting to each other. In this article, we report which-way-2D-cross-double-slit experiments by detecting which slit of a double-slit of 2D-cross-double-slit apparatus a photon would pass through. The experimental results show that photons passing through the detected double-slit behave as particle, while photons passing through other undetected double-slit(s) distribute as wave in the same experiment with the same apparatus. Namely the particle nature and wave distribution coexist, which violates Bohr¡¯s complementarity principle. We suggest that photon¡¯s ¡°particle nature¡± is intrinsic, while the term ¡°wave nature¡± represents a wave-like distribution, which is a consequence of movement of photon as particle. It is a challenge to interpret mathematically those observations consistently. http://pubs.sciepub.com/ijp/8/4/6/ijp-8-4-6.pdf which-way-double-slit experiment which-way-cross-double-slit experiment wave-particle duality complementarity principle cross-double-slit experiment quantum mechanics