About Part one Editorial Board of the journal Thermal Science consistently follows the policy to prepare issues devoted to the specific, modern scientific topics. Having eminent guest editors, and thanks to their agility and efforts we had in the past several years a number of excellent special issues devoted to a wide scope of topics. This time, our most active Guest editor Prof. Jordan Hristov, proposed an extremely interesting topic – Fractional calculus to Heat, Momentum and Mass Transfer Problems. Last year we had also an excellent special issue devoted to analytical methods in thermal sciences, with a nice set of papers chosen by Prof. Ji-Huan He. Present selection of eleven papers devoted to fractal calculus made by Prof. Hristov in Part I, No. 2, 2012, gives nice insight into the capabilities of this scientific tool in solving problems in heat, mass, and momentum transfer. This can be clearly seen not only by reading papers in Part I of this issue, but also from the nice preface written by Prof. Hristov. I am deeply grateful to the Guest editor, Prof. Jordan Hristov (Department of Chemical Engineering, University of Chemical Technology and Metallurgy, Sofia, Bulgaria), not only for proposing this topic and for excellent paper selection, but also for permanent care to improve the journal Thermal Science, and to ensure that topics of the published paper are of the current scientific interest. The journal Thermal Science will try, in the future issues also, to make a balance between numerical and analytical methods for modeling processes in thermal sciences, in order to present to the readers a wide scope of possible approaches.