Future instrumentation for the study of the Warm-Hot Intergalactic   Medium
  We briefly review capabilities and requirements for future instrumentation in UV- and X-ray astronomy that can contribute to advancing our understanding of the diffuse, highly ionised intergalactic medium. 
F.B.S. Paerels, J.S. Kaastra, T. Ohashi, P. Richter, A.M. Bykov, J.   Nevalainen