I will discuss a localized Big Bang formation result, for the Einstein-nonlinear scalar field equations, without symmetry assumptions and that does not require the initial data to be close to any fixed background solution. The key new ingredient for the proof is the introduction of a new gauge for Einstein's equations. This gauge has two advantages over the one used in previous localized Big Bang stability results. First, it is independent of the matter model, so it is possible that it can be used to prove Big Bang formation in the absence of a scalar field. And second, it is suitable to prove that the solutions induce geometric initial data on the singularity, thus providing a complete description of the asymptotics near the Big Bang.