title: Apply a function over a list of lists of dataframes in R
body: <p>I've a nested structure like:</p>
  
  <ul>
  <li>A parent list 'parent' made of a variable number of items</li>
  <li>Each node of the parent list is a list of three named elements (let's say 'foo',
  'bar', 'puppy')</li>
  <li>These (named) elements of the inner list are dataframes made of a variable number of columns</li>
  </ul>
  
  <p>(it's even difficult to me to build a reproducible example of this structure, actually)</p>
  
  <p>I'm searching an effective way to apply a function (let's say toLower) to each cell of the inner dataframes, ofc for each element of the parent list.</p>
  
  <p>I think I could nest some lapply but I have no idea on how to reference the inner elements and which FUN to use as lapply parameter itself</p>