Mesh : resolving a part much thinner than the rest of the volumes

Hi,

I don't know much about the different options for meshes and their mechanism of creation. I am studying a geometry where the is a layer much thinner than the rest of the geometry. 1cm becomes 1 micrometer on this layer, where the temperature will vary very fast ( time dependent study of a few microsecondes).

I try different options without really knowing their impact. Sometimes the mesh can't be created because the smallest element size is too large and if I bring it down enough, I end up with meshes with far too many points and it slows the calculation.

Do you have any advice for me ?
For example, how could I get elements much larger in two directions than in the third one ?

Thank you very much
Simon