  Aperiodic order refers to the mathematical formalisation of quasicrystals.
Substitutions and cut and project sets are among their main actors; they also
play a key role in the study of dynamical systems, whether they are symbolic,
generated by tilings, or point sets. We focus here on the relations between
quasicrystals and self-similarity from an arithmetical and dynamical viewpoint,
illustrating how efficiently aperiodic order irrigates various domains of
mathematics and theoretical computer science, on a journey from Diophantine
approximation to computability theory. In particular, we see how Pisot numbers
allow the definition of simple model sets, and how they also intervene for
scaling factors for invariance by multiplication of Meyer sets. We focus in
particular on the characterisation due to Yves Meyer: any Pisot or Salem number
is a parameter of dilation that preserves some Meyer set.
