We measured heat flow processes near the melting point of a typical ionic liquid, 1-butyl-3-methylimidazolium bromide ([C(4)mim]Br), using a laboratory-made differential scanning calorimeter with the base line stability of +/- 3 nW. We discovered the rhythmical exothermic and endothermic processes with the time scale of 10(1) s in the pre-melting region and in the region just after melting. This novel phenomenon is attributed to the link of the melting/crystallizing in domains and cooperative conformational change of the [C(4)mim](+) ion. It is also confirmed that about 10(12)-10(13) ion pairs of [C(4)mim]Br are involved in the domains. (C) 2008 Elsevier B.V. All rights reserved.