Exact Results in Quantum Theory

I will speak about recent results on the two-loop and three-loop contributions to the Lamb shift in hydrogen. In particular, I will speak about a missing term in order $\alpha^2(Z\alpha)^6m\log(Z\alpha)$, about non-logarithmic contributions in the same order, and about the estimation of the three-loop term of order $\alpha^3(Z\alpha)^5m$. Together with a recent result of Laporta of order $\alpha^4(Z\alpha)^4m$ that makes evaluation of the all $\alpha^8m$ contributions complete.