In this paper, a uniform calf thymus deoxyribonucleic acid (DNA) network has been constructed on a bare mica surface using a simple adsorption method. The effect of the immersion time in water on the characteristics of the morphological transitions of DNA molecules adsorbed on the mica surface was investigated by atomic force microscopy. It was found that the DNA molecules underwent conformational transitions from stretched wormlike coil to rod and to network by changing the immersion time in water and the formation mechanism was explained briefly. (C) 2008 Elsevier B.V. All rights reserved.