  Utilizing {\it ab initio} ultra-high resolution hydrodynamical simulations,
we investigate the properties of the interstellar and circum-galactic medium of
Ly$\alpha$ Blobs (LABs) at $z=3$, focusing on three important emission lines:
Ly$\alpha$ 1216\AA, \heii 1640\AA\ and \civ 1449\AA. Their relative strengths
provide a powerful probe of the thermodynamic properties of the gas when
confronted with observations. By adjusting the dust attenuation effect using
one parameter and matching the observed size-luminosity relation of LABs using
another parameter, we show that our simulations can reproduce the observed
\civ/\lya\ and \heii/\lya\ ratios adequately. This analysis provides the first
successful physical model to account for simultaneously the LAB luminosity
function, luminosity-size relation, and the \civ/Ly$\alpha$ and
\heii/Ly$\alpha$ ratios, with only two parameters. The physical underpinning
for this model is that, in addition to the stellar component for the \lya\
emission, the \lya\ and \civ\ emission lines due to shock heated gas are
primarily collisional excitation driven and the \heii\ emission line
collisional ionization driven. We find that the density, temperature and
metallicity of the gas responsible for each emission line is significantly
distinct, in a multi-phase interstellar and circumgalactic medium that is
shock-heated primarily by supernovae and secondarily by gravitational accretion
of gas.
