It is a great pleasure to have possibility to publish papers written by young scientists, even more if they have already been recognized by the international scientific community. We have honor to open 1st issue of the journal Thermal Science in 2012, with an interesting essay written by Marko Popović: There are two twin shadows, but Einstein is one. this essay is a shortened version of his paper: The Fairytale about the Old and Young Twin and its Thermodynamic Solution, presented last year at the 66th North American Calorimetry Conference (CALCON 2011), held in June 2011 at Kahuku, Oahu, Hawaii, USA, and awarded by The William F. Giauque Memorial Award. professor William F. Giauque received the 1949 Nobel Prize in Chemistry for his contributions in thermodynamics, and the William F. Giauque Memorial Award was established to recognize his outstanding mentoring ability by encouraging student participation at the Calorimetry Conference. Marko Popović is presently a student of the Faculty of Chemistry at the University of Belgrade in Serbia. From his scholar days he has been showing an enthusiastic interest to think and analyze philosophical and physical mysteries of the thermo dynam ics, both, reversible and irreversible, relativistic and non-relativistic, and has published several papers in scientific journals and gave his contributions to the scientific conferences. Thermal Science Editorial Boards, recognizing scientific interest of Marko Popović, and with the aim to support his further scientific development, published a few years ago his fascinating, intriguing, and controversial contributions, when he was yet in secondary school (Laying the Ghost of Twin Paradox, Thermal Science, Year 2009, Volume 13, Issue 2, pp. 217-224 and Equation of State in Form which Relates Mol Fraction and Molarity of Two (or More) Component Thermodynamic System Consisted of Ideal Gases, and It's Applications, Thermal Science, Year 2010, Volume 14, Issue 3, pp. 859-863). By publishing his new paper as the first one in this issue, we congratulate him for his scientific progress.