This is an image from Sam's biopsy of his small intestine.  Notice the
underdeveloped, unorganized structure of the microvilli on the outer edge
of the cell.  The black arrow in the image points to microvilli that are being
included inside the cell instead of the outer edge.(Click image for larger
view)
This is an image of a normal intestinal cell.  Notice the tightly packed,
orderly hairlike structure that line the outer edge of the cell (Click image
for larger view).
What is Microvillus Inclusion Disease?
Sometimes it is hard to remember the days when we didn't know what microvilli, bilirubin, TPN, Omegaven, or a Broviac  were.  When people ask us what
Microvillus Inclusion Disease is I have a feeling most times people walk away with our answer being more confused than they were before they asked.  
For that reason, we have posted an over simplified answer to this question here.  If you would like to read more information, the link below will perform a
Google search for recently updated information regarding Microvillus Inclusion Disease.  Be warned, most of the information out there is highly technical
and can be a bit depressing when it comes to prognosis.

What Microvillus Inclusion Disease means for Sam, in the most basic way, is that his intestines do not work properly.  His intestines do not absorb
nutrients like most people and he has to be supplied with all of his nutrition through an IV.  In Sam's case this is done in a central line that starts at a spot
on the right side of his chest, tunnels under his skin to a vein in his neck and then travels down that vein to a spot close to his heart.

In slightly more detail, the cells in the intestine are normally lined with small hair like structures called microvilli. These structures are what  do the actual
absorbing of nutrients in your intestines.
Search using Google for recent Microvillus Inclusion Disease posts:

Google Search for Microvillus Inclusion Disease

A much more technical description of Sam's disease can be found here:

http://emedicine.medscape.com/article/928100-overview