Abstract: I will introduce a new type of boundary condition in JT gravity, that corresponds to studying the theory on finite geometries with a fluctuating boundary. This provides a completely new, microscopic, perspective on the model and opens up several avenues of research, the main points of which I will outline in my talk. In particular, I will describe a discretized formulation of the theory, corresponding to a new combinatorial problem in enumerative geometry, on which progress has been made very recently. I will also describe a purely continuum approach, making an unexpected link with Liouville theory techniques. The picture that emerges provides a fully quantum formulation of the notion of finite cut-off in holography, making a link with old ideas based of end-of-the-world Randall-Sundrum branes, and suggesting a model of emerging absolute boundary time.