If by "enters it" you mean crossing the event horizon, then the easy answer is: we'll never know. No signal can reach us from the probe since photons can't escape. By definition the "material," if there is such a thing, at the center of a black hole is inside the event horizon. So the last signal you will get from the probe will be just before it crosses the event horizon. The time dilation noted in another answer here results in the signal being Doppler shifted to lower and lower frequencies, with the encoded data going to lower and lower data rates, and the intensity going down rapidly until you receive the last photon from the probe as it dims to nothing.
For supermassive black holes, spaghettification will not occur until after crossing the event horizon, so you can survive an approach to the event horizon.
Interestingly, what happens when you cross the event horizon is a subject of great debate. When considering the quantum mechanics and quantum information transfer at the event horizon of a black hole, it all becomes very complicated. You might make it across uneventfully (pun intended), or you might be completely destroyed right at the event horizon. See this excellent blog post for a discussion of the current debates.
The event horizon is defined as the distance from the center of the black hole at which the gravitational escape velocity equals the velocity of light. Therefore, given that the speed of light is a universal speed limit, nothing inside of the event horizon can ever escape. That distance for a simple, non-rotating black hole is called the Schwarzschild radius, equal to $2\mu\over c^2$. $\mu$ is the standard gravitational parameter for the mass of the black hole $M$, $\mu=GM$, and $c$ is the speed of light. If the Earth were somehow compressed into a black hole, its Schwarzschild radius would be about 1 cm.