  A novel concept of quantum turbulence in finite size superfluids, such as
trapped bosonic atoms, is discussed. We have used an atomic $^{87}\mathrm{Rb}$
BEC to study the emergence of this phenomenon. In our experiment, the
transition to the quantum turbulent regime is characterized by a tangled vortex
lines formation, controlled by the amplitude and time duration of the
excitation produced by an external oscillating field. A simple model is
suggested to account for the experimental observations. The transition from the
non-turbulent to the turbulent regime is a rather gradual crossover. But it
takes place in a sharp enough way, allowing for the definition of an effective
critical line separating the regimes. Quantum turbulence emerging in a
finite-size superfluid may be a new idea helpful for revealing important
features associated to turbulence, a more general and broad phenomenon.
