Contemporary notes on metamaterials

The essence of the metamaterial concept from the structural point of view. Particular attention is paid to the macroscopic description of metamaterials and to the corresponding requirements and precautions for using that concept. General advantages of metamaterials are also pointed out. Next, the main research directions related to metamaterials are briefly overviewed and the key references are provided. Finally, the most probable sources of disagreement and misunderstanding within the field are summarised.