In Brian Greene's book The Elegant Universe he goes to some lengths to describe Lineland, inhabited by Linebeings, this being a one-dimensional world with one-dimensional things in it. While he's describing the analogy of Lineland, he brings a doctor to a Linebeing and describes the doctor as "reaching inside your exposed interior".
This book is great and covers a lot of ground on string theory and the science preceding it, which is always useful since it doesn't matter how many times you read about quantum mechs or from whose perspective, there's something else to be considering in it. Yet it springs to mind that a one-dimensional being won't have an interior to reach into. Since the brain operates naturally on a 3D format, it's understandably difficult to conceptualise other dimensions.
Kaluza was an unknown mathematician from Poland who added one dimension to Einstein's 3D+Time formula and found in doing so that he had replicated Maxwells' equation given in the 1880s to describe electromagnetism. After initial enthusiasm and a couple of changes of heart, it subsequently took Einstein 2 years to approve the concept for publication. 6 decades later, after unilateral dismissal from scientists chasing collaboration to create the Standard Model, more information had led to more questions and in the mid 1970s higher-dimensional research was again underway.
Where are we now? In connceptualising dimensions, are things getting any easier?