botany question

I have a botany question maybe someone out there can
help.
Thinking about growing food in space, I remember
seeing this on so many science shows. The scientist
would take some plant cells, I think from leafs and
place them in this medium which would cause them to
grow like this green blob, no leaf, no roots almost
like undefined algae. Then they would do something and
roots or shoots would grow.
Does anyone know what this medium is? I figure it may
be cost effective to just grow certain veggies this
way and not use any soil at all and not have the root
and stem part to toss out.
thank You
Pete