The physical quantity "temperature" is a cornerstone of thermodynamics and
statistical physics. But it is necessary to mention that very frequently the
scientists forget about the conditions to be satisfied in order to introduce
"temperature" in macroscopic physics. In the present paper the short
introduction to the classical concept of temperature for macroscopic
equilibrium systems will be given. The concept of "spin temperature" in
condensed matter physics will be reviewed and the advantages of thermodynamic
approach to the problems of magnetism will be illustrated. Finally, the concept
of temperature will be discussed regarding the nanoscale physics and
non-extensive systems.Comment: 4 figures, InTech class file included, accepted for publication in
"Thermodynamics - Systems in Equilibrium and Non-Equilibrium" ISBN
979-953-307-047-5, edited by J. C. M. Piraj\'a
