[paul cotter (OP)]

In electromagnetics the following identity is very useful: ∇x∇xA=grad(divA)-laplacianA. Things like divergence, curl and gradient are easily visualised as outflow, rotation and directional rate of change but I cannot visualise the "curl of a curl of a function". I need a mental visualisation or construct to get a full understanding but I realise this is not always possible as some maths is too abstract to enable a mental picture. Any thoughts?