In this report we studied structural compaction of a genomic DNA, an important mechanism for the chromatin condensation, in a nano-space of an anionic AOT (bis(2-ethylhexyl)sulfosuccinate) reverse micelles (RM). The homo-molecular picosecond-resolved fluorescence resonance energy transfer (FRET) studies on the DNA-bound acridine orange encapsulated in the RM indicate that the DNA in the nano-space is condensed and shows an insignificant dependency of the structural compaction of the DNA on the degree of hydration (wo) of the microenvironment. The circular dichroism (CD) spectrum shows that condensed DNA assumes the psiform. (c) 2005 Elsevier B.V. All. rights reserved.