Hammerhead ribozyme is the smallest naturally occurring catalytic RNA. It is a perfect model for structure-function relation studies. Initially, it was identified as an autocatalytic part of viroid and virusoid genomic RNA. It exists within the genomes of many organisms including human, which makes it the most common autocatalytic motif in the nature. After 25 years of intensive research, there are a lot of data considering its structure, conformational dynamics and an influence of tertiary stabilizing motifs on its stability and properties. Structure of the hammerhead ribozyme is a system of elements that influence each other. The knowledge of ribozyme architecture is outstandingly interesting in the context of rules and logic of design, construction and application of such molecules as spatial molecular constructions. Presence of additional structural motifs distinguishes extended hammerhead ribozyme from the minimal one. Hammerhead ribozyme recognizes complementary RNA and catalyses transesterification after the 5'-NUH-3' sequence. Reaction efficiency depends on an arrangement of atoms of the catalytic core presence of metal ions and other intracellular factors. Innovative and potentially better derivatives of the hammerhead ribozyme are objects of extensive research in the field of molecular medicine.