Many ideas have been suggested to extend the standard cosmology. This thesis gives brief overviews of three kind of them. Firstly, models with extra dimensions are presented. This idea does not solve longstanding problems in particle physics but also gives possibility of reproducing the standard cosmology in higher dimensional space-time than usual 4-dimensional. Secondly, the holographic principle is summarized. Originally, it was a conjecture from black holes thermodynamics. Now we have the most generalized form, Bousso`s version, which is ready to apply various space-times. The holographic principle was tested by AdS/CFT correspondence which has been developed independently in string theory. Thirdly, the anthropic principle is reviewed. It has been developed purely in phenomenological speculation. Especially, the cosmological constant problem could be addressed by the anthropic argument. The anthropic principle gives possibility of solving remaining problems in the standard cosmology.