  We introduce a scheme for deep laser cooling of molecules based on robust
dark states at zero velocity. By simulating this scheme, we show it to be a
widely applicable method that can reach the recoil limit or below. We
demonstrate and characterise the method experimentally, reaching a temperature
of 5.4(7) $\mu$K. We solve a general problem of measuring low temperatures for
large clouds by rotating the phase-space distribution and then directly imaging
the complete velocity distribution. Using the same phase-space rotation method,
we rapidly compress the cloud. Applying the cooling method a second time, we
compress both the position and velocity distributions.
