  We study the soft X-ray emission (0.1 - 1 keV) from the Warm-Hot
Intergalactic Medium (WHIM) in a hydrodynamic simulation of a Cold Dark Matter
universe. Our main goal is to investigate how such emission can be explored
with a combination of imaging and spectroscopy, and to motivate future X-ray
missions. We first present high resolution images of the X-ray emission in
several energy bands, in which emission from different ion species dominates.
We pick three different areas to study the high resolution spectra of X-rays
from the warm-hot IGM: (a) a galaxy group; (b) a filament and (c) an
underluminous region. By taking into account the background X-ray emission from
AGNs and foreground emission from the Galaxy, we compute composite X-ray
spectra of the selected regions. We briefly investigate angular clustering of
the soft-X-ray emission, finding a strong signal. Most interestingly, the
combination of high spectral resolution and angular information allows us to
map the emission from the WHIM in 3 dimensions. We cross-correlate the
positions of galaxies in the simulation with this redshift map of emission and
detect the presence of six different ion species (Ne IX, Fe XVII, O VII, O
VIII, N VII, C VI) in the large-scale structure traced by the galaxies. Finally
we show how such emission can be detected and studied with future X-ray
satellites, with particular attention to a proposed mission, the Missing Baryon
Explorer, or MBE. We present simulated observations of the WHIM gas with MBE.
