  The interstellar medium feeds both the formation of stars and the growth of
black holes, making it a key ingredient in the evolution of galaxies. With the
advent of the Atacama Large Millimeter/ submillimeter Array (ALMA), we can now
probe the interstellar medium within high-redshift galaxies in increasingly
exquisite detail. Our recent ALMA observations map the molecular gas and dust
continuum emission in sub-millimetre-selected galaxies on 1-5 kpc scales,
revealing significant differences in how the gas, dust continuum, and existing
stellar emission are distributed within the galaxies. This study demonstrates
the power of ALMA to shed new light on the structure and kinematics of the
interstellar medium in the early Universe, suggesting that the interpretation
of such observations is more complex than typically assumed.
