I Encounter på Farpoint Data berättar Riker att mycket av vad de interagerar med i holodeck är faktiskt replikerad materia och inte hologram.
RIKER: I didn't believe these simulations could be this real.
DATA:Much of it is real, sir. If the transporters can convert our bodies to an energy beam, then back to the original pattern again
RIKER: Yes, of course. And these rocks and vegetation have much simpler patterns.
I samma scen faller Wesley i ström och är fortfarande fuktig när han lämnar holodeck.
WESLEY: Sir, maybe I should get something to wipe this water up.
PICARD: Good idea.
Och från Memory Alphas Holodeck -sida:
In the early 24th century, matter replication was primarily used for objects and characters that would be in direct contact with the occupants which gave them an extreme sense of realism. Water, for example, would feel like actual water because on some level, it was, and it could create experiences like odors. This also enabled simple matter to exist outside of the holodeck for brief periods of time (such as snow) before they would lose cohesion without the support of the holodeck grid and revert back to energy.
This, however, used an extreme amount of power, and caused repetitive problems to occur in its safe usage. Some time in the mid 24th century, this was slowly phased out in favor of simpler 'true' holographic technology by focusing on the photons contained within micro force fields. This was not only safer and used less power, but had more varied usage and could be easily controlled with quicker reaction times. Some would argue this made it lose its appeal, but advances in the technology has made it as real as the matter replication method, which is still used for more complex, tactile objects, as well as food, odors, etc.