We propose a method to study lattice QCD at finite temperature (T) and chemical potential (\mu). We test the method and compare it with the Glasgow method using n_f=4 staggered QCD with imaginary \mu. The critical endpoint (E) of QCD on the Re(\mu)-T plane is located. We use n_f=2+1 dynamical staggered quarks with semi-realistic masses on L_t=4 lattices. Our results are based on {\cal{O}}(10^3-10^4) configurations.