Using atomic force microscopy, full visualization of a single giant T4 DNA molecules (166 kilo base pairs), the contour length of which is sufficient to examine the scaling property, was achieved. Fluorescence microscopic measurement was performed on exactly the same T4 DNA molecules. The results showed that there are three distinguishable regions in the scaling property Rsimilar toL(nu), where R, L, and nu are the end-to-end distance, contour length and scaling exponent, respectively: (i) nusimilar or equal to1 when L<0.10 mum, (ii) nusimilar or equal to0.5 when 0.10 mum4 mum. This conformational behavior is discussed in relation to self-avoiding walk in 2D.