Even surfaces that feel smooth at the macroscopic scale have roughness at the microscopic level. These tiny bumps and valleys can interact with each other, creating friction even between seemingly smooth surfaces.

Here are some factors that contribute to friction between two smooth surfaces:

1. Adhesion: When two surfaces are brought into contact, their atoms and molecules can interact and form temporary bonds. These bonds are weak, but they can create a resistance to motion, resulting in friction. The stronger the adhesion, the greater the friction.

2. Deformation: When two surfaces slide past each other, the bumps and valleys on their surfaces can deform and interlock. This can hinder their movement, creating friction. The harder the surfaces are, the more resistant they are to deformation, and therefore, the less friction they will generate.

3. Elasticity: The elasticity of the surfaces can also influence friction. Elastic materials can deform and then return to their original shape when the force is removed. This elasticity can help to reduce friction because it allows the surfaces to conform to each other's irregularities and reduces the interlocking effect.

In summary, the microscopic roughness, adhesion, deformation, and elasticity of surfaces can all contribute to friction between two seemingly smooth surfaces.