  We review versions of the Generalized Uncertainty Principle (GUP) obtained in
string theory and in gedanken experiments carried out in Quantum Gravity. We
show how a GUP can be derived from a measure gedanken experiment involving
micro-black holes at the Planck scale of spacetime. The model uses only
Heisenberg principle and Schwarzschild radius and it is independent from
particular versions of Quantum Gravity.
