Iron is the most abundant transition metal in our body and plays various pivotal roles in our lives including oxygen transport, energy production, and metabolic reactions. At the same time, an excess amount of iron may cause cellular damages through undesired oxidative reactions due to the high redox activity of Fe ion. We have developed the several fluorescent probes which can detect Fe(II) ion selectively with fluorescence enhancement to understand both the physiological and pathological contributions of Fe ion in living systems. These fluorescent probes worked in an aqueous buffer, living cells, and histochemical-stained samples (Chem Sci. 2013;4:1250, Chem Sci. 2017;8:4858, Free Radic Res. 2014;48:990, Sci Rep. 2017;7:10621). We established a color series of Fe(II)-selective fluorescent probes from blue to deep-red, which were applied to organelle-targeted fluorescent probes for mitochondria, lysosome, and endoplasmic reticulum. Herein, I would like to focus on fluorescence imaging study about the alteration of labile Fe(II) level in each organelle during ferroptosis, iron-dependent cell death, by using the various organelle-targeted fluorescent probes of Fe(II).