Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology. For producing a picture MRI scanners use strong magnetic fields from 0.2 to 7 Tesla, electromagnetic waves and field gradients.The basic principle for getting a signal is the interaction between magnetic moments of hydrogen atoms and energy from electromagnetic pulse in the radio frequency spectrum (RF pulse). The body is placed into a strong magnetic field which induces longitudinal magnetization in the body. Then we apply a RF pulse which tilts magnetization into a plane that is perpendicular to our external magnetic field and that magnetization is now called trasnversal magnetisation. The signal that is arising from the body now becomes measurable. After the application of RF pulse, tilted magnetization starts to return to its steady state. Because the magnetization in motion induces electric currency, we are able to measure the signal. That process of magnetization returning to steady state is called relaxation. We have two types of relaxation, T1 and T2, and those are parameters that affect the outcome of the final image. Depending on how long the relaxations are, we will have different signal and also the different image from different tissues. Combining different energy or duration of the RF pulse we can alter the picture result so it will be more in the area of T1 or T2 relaxation. Those areas of relaxation are called T1-weighted or T2-weighted images and help us in better differentiation of the tissues. Localisation of the signal arising from the body is done through gradient magnetic fields. Magnetic resonance imaging is a non-ionising procedure which vastly improves our opportunities for better diagnostics. The only contraindications to this type of imaging are non-removable metal implants. The advanced functionality of MRI in body imaging gives it a irreplaceable role in modern medicine.