We will show certain physical characteristics that leads to strong 
near-field field enhancement in plasmonic  nanostructures using 
collective resonances. The structures considered generally involve two 
or a collection of plasmonic nanosctarrers, that sometimes are arrayed 
or clustered to generate even stronger collective resonance.
Based on simulations, strong field enhancement will be related to 
possible enhancement of the excitation and emission rate of organic 
molecules besides clustered structures. The possibility to generate 
enhancement of local magnetic fields at optical wavelengths is also 
discussed showing some examples.