  We present a 3D MHD simulation of two merging flux ropes exhibiting
self-generated and self-sustaining turbulent reconnection (SGTR) that is fully
3D and fast. The exploration of SGTR is crucial for understanding the
relationship between MHD turbulence and magnetic reconnection in astrophysical
contexts including the solar corona. We investigate the pathway towards SGTR
and apply novel tools to analyse the structure and topology of the reconnection
layer. The simulation proceeds from 2.5D Sweet-Parker reconnection to 2.5D
nonlinear tearing, followed by a dynamic transition to a final SGTR phase that
is globally quasi-stationary. The transition phase is dominated by a kink
instability of a large "cat-eye" flux rope and the proliferation of a broad
stochastic layer. The reconnection layer has two general characteristic
thickness scales which correlate with the reconnection rate and differ by a
factor of approximately six: an inner scale corresponding with current and
vorticity densities, turbulent fluctuations, and outflow jets, and an outer
scale associated with field line stochasticity. The effective thickness of the
reconnection layer is the inner scale of the effective reconnection electric
field produced by turbulent fluctuations, not the stochastic thickness. The
dynamics within the reconnection layer are closely linked with flux rope
structures that are highly topologically complicated. Explorations of the flux
rope structures and distinctive intermediate regions between the inner core and
stochastic separatrices ("SGTR wings") are potentially key to understanding
SGTR. The study concludes with a discussion on the apparent dualism between
plasmoid-mediated and stochastic perspectives on SGTR.
