The aim of the work is to provide a stable method to get sharp bounds for Boltzmann and Landau operators in weighted Sobolev spaces and in anisotropic spaces.  The results and proofs have the following main features and innovations:

All the sharp bounds are given for the original Boltzmann and Landau operators.
The sharpness means the lower and upper bounds for the operators are consistent with the behavior of  the linearized operators. Moreover, we make clear the difference between the bounds for the original operators and those for the linearized ones. It will be useful for the well-posedness of the original equations.
According to the Bobylev's formula, we introduce two types of dyadic decompositions performed in both phase and frequency spaces  to make full use of the interaction and the cancelation. It allows us to see clearly which part of the operator behaves like a Laplace type operator and which part is dominated by the anisotropic structure. It is the key point  to get the sharp bounds in weighted Sobolev spaces and in anisotropic spaces.
Based on the geometric structure of the elastic collision, we make a geometric decomposition to capture the anisotropic structure of the  collision operator. More precisely, we make it explicit that the fractional Laplace-Beltrami operator  really exists in the structure of the collision operator. It enables us to derive the sharp bounds  in anisotropic spaces and then complete the entropy dissipation estimates.
The structures mentioned above are  so stable that we can apply them to the rescaled Boltzmann collision operator in the process of the grazing collisions limit. Then we get the sharp bounds for the Landau collision operator by passing to the limit.  We remark that our analysis used here will shed light on the investigation of the asymptotics from Boltzmann equation to Landau equation.