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Over the past decades, cell-based biosensors have been developed for various applications, such as pharmaceutical screening, environmental monitoring, and toxin detection. Among different cell-based assays, electrochemical impedance spectroscopy (EIS) using microelectrode arrays has emerged as a promising label-free method for detecting cellular responses to toxins of chemical or biological origin. Despite the documented success in the EIS measurement of the impedance time series and the derivation of the half-inhibition concentration, the application of EIS for cytotoxicity assessment can go considerably beyond this. Here, we applied electric cell-substrate impedance sensing (ECIS) to study cell behavior electrically. In this method, cell layers are cultured on small gold film electrodes, and the electrical impedance of the cell-covered electrode is measured as a function of frequency and time. We can acquire both junctional resistance and average cell-substrate separation by comparing the experimental data with the calculated values obtained from a proper cell-electrode model. ECIS can be used to quantify changes in cell morphology and motility with exquisite sensitivity and in a non-invasive manner, resulting in a significant profit in many areas of cell research, including the dynamics of cell attachment and spreading, the barrier function of endothelial and epithelial layers, in vitro toxicology and the metastatic potential of cells. In this talk, in addition to the general characteristics of ECIS, I will emphasize the in vitro assessment of cytotoxicity and the detection of trans-endothelial invasion of human ovarian carcinoma cells in culture. I will also discuss the challenges and opportunities of using ECIS for TEER and Trans-filter invasion measurements. The analytical methods used in these studies can serve as model approaches for ECIS and other EIS-based biosensors to investigate various features of cell behaviors in tissue culture.