High power electromagnetic signals can disrupt the functioning of electronic devices. As electromagnetism plays a role in cells homeostasis, such electromagnetic signals could potentially also alter some physiological processes. Herein we report on distinct biological parameters assessment after cellular spheroids exposure to high power electromagnetic signals, such as the ones used for defense applications. Signals effects were assessed in tumor cells spheroids and in normal human dermal fibroblasts spheroids, where macroscopic aspect, growth, plasma membrane integrity, induction of apoptosis, ATP content, and mitochondrial potential were investigated after spheroids exposure to high power electromagnetic signals. No significant effects were observed, indicating that 1.5 GHz narrowband electromagnetic fields with incident amplitude level of 40 kV/m, and 150 MHz moderate-band electric fields with an amplitude of 72.5 to approximately 200 kV/m, do not cause any significant alterations of assessed parameters. Electronic devices can stop operating in response to intense external electromagnetic signals. Electromagnetic environments, or more precisely intentional electromagnetic environments 1 , are among emerging approaches that could be used for defense applications. High power electromagnetic (HPEM) technology can be deployed to temporarily or permanently disrupt electronic devices or could even be used against the personnel 2. The HPEM systems that can be used to impair or destroy electronics and hardware 3 , and thus to black out the opponents electronic systems, operate in the range of tens of MHz to a few tens of GHz. Alternatively, HPEM signals (with frequencies of approximately 100 GHz and millimeter waves) could be used against personnel. This non-lethal directed-energy weapon, can heat the surface of its targets (e.g. heat people's skin) 2. Such non-lethal weapon system, also known as the Active Denial System, was developed by the U.S. military (https://jnlwp.defense. gov/Press-Room/Fact-Sheets/ArticleViewFactsheets/Article/577989/active-denial-technology-fact-sheet/ retrieved August 2018) and was designed for area denial, perimeter security and crowd control. Similar systems were also elaborated by Russia (https://www.popularmechanics.com/military/weapons/a7804/ why-russia-will-be-the-first-to-use-the-pain-ray-9833954/ retrieved August 2018) and China (http://en.people. cn/n3/2018/0205/c90000-9423875.html retrieved August 2018). High Power Microwave (HPM) and High Power Radio Frequency (HPRF) systems can radiate high power and short duration oscillatory pulses of electromagnetic fields. These pulses can exhibit different amplitudes, durations, frequency spectrums, as well as Pulse Repetition Frequencies (PRF), and can be classified into different families, according to their frequency spectrum bandwidth. The bandwidth classification distinguishes the narrowband (also known as hypo band), meso (or moderate) band, ultra-moderate (or sub-hyper) band and hyperband intentional electromagnetic environments 2 .