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Transition-metal dichalcogenide IrTe₂ has attracted extensive attention because of its intriguing structural transitions, abnormal resistivity, and superconductivity. While it forms a trigonal phase at room temperature, the structure below the phase transition at 280 K is is still in debate. With in-situ transmission and scanning transmission electron microscopy (STEM), we study the phase transitions of IrTe₂ single crystal from room temperature down to 20 K. The electron diffraction and imaging results show that IrTe₂ below 280 K is phase separated, with the coexistence of the well-characterized 5 × 1 × 5 phase, an intergrowth phases with multiple modulated vectors, and the remaining trigonal phase. The 5 × 1 × 5 phase is present down to 20 K, but we never observe the 6 × 1 × 6 or 8 × 1 × 8 phase previously reported. The valence states of IrTe₂ for different phases have been investigated by electron energy loss spectroscopy. A clear picture of the temperature-dependent structural evolution of bulk IrTe₂, which is essential to understand the unique electric and magnetic behaviors, will be presented.