Application of jet schemes to singularities in positive characteristic. Recently "Mather-Jacobian discrepancy" is introduced, which is an analogy of usual discrepancy. We can classify singularities by means of MJ-discrepancy, in the similar way as usual discrepancy. One advantage of MJ-discrepancy is that is is well described by jet schemes in arbitrary characteristic (joint work with A. Reguera). In the talk I will pose some conjectures about jet schemes and show that these yield basic properties of singularities of positive characteristic. And then I will show that in lower dimensional singularities, the conjectures hold.