Building together a “ <i>trencadís”</i> of nucleotide metabolism

The 21^th biennial symposium on Purine and Pyrimidine metabolism (PP25) was organized by the Purine and Pyrimidine Society (PPS) in June 2025. The symposium took place in Barcelona, Spain, and the chairman was Prof. Marçal Pastor-Anglada affiliated to the University of Barcelona. The scientific program covered various topics such as inborn errors, cancer, immunity, enzymatic reactions, drug development etc. and was presented in 8 sessions over three days. The current issue of <i>Nucleosides, Nucleotides & Nucleic Acids</i> is a collection of articles issued from PP25-presentations and other PPS-related manuscripts, and in this editorial, we give an overview of the scientific program of the meeting.