Mitochondrial ribosomes, or mitoribosomes, are responsible for synthesis of mitochondrial membrane proteins. The structures of the large subunit (39S) from porcine and human mitoribosomes were described in 2014. Now the same investigators complete the picture with the structures of the full 55S mitoribosome. Amunts, Brown et al. determined the structure of the human mitoribosome at 3.5-Å resolution by cryo-EM and observed nascent polypeptide being folded in the exit tunnel. Greber, Bieri, Leibundgut et al. presented the cryo-EM structure of the small subunit (28S) of the porcine mitoribosome at 3.6-Å resolution and an atomic model of the entire mitoribosome with mRNA and tRNAs bound, based on a 3.8-Å cryo-EM map and data from cross-linking and MS analysis. The findings from both groups confirmed that the mammalian 55S mitoribosome is very different from its bacterial 70S counterpart, with a reduced rRNA core and numerous ribosomal proteins covering the surface almost completely. The small and large subunits interact less extensively than in bacterial 70S, to result in increased conformational flexibility. In fact, the small subunit could be observed in different orientations by both groups. The mRNA channel, responsible for binding leaderless mitochondrial transcripts, features remodeled entry and exit sites. Finally, the structures explain why certain polymorphisms in the mammalian mitoribosome rRNA lead to hypersensitivity to aminoglycoside antibiotics: those mutations allow base-pairing that would yield a mitoribosome more similar to the bacterial one and restore the binding pockets for aminoglycosides. (Science 348, 95–98, 2015; Science doi:10.1126/science.aaa3872, 2 April 2015)