This digital resource is a scientific article from the Journal of Microscopy, providing a simple introduction to multiphoton microscopy. Multiphoton microscopy, including two-photon excitation, is a powerful optical imaging technique that allows for deep tissue imaging with reduced phototoxicity and photobleaching compared to conventional fluorescence microscopy. The article aims to demystify the complex quantum mechanical effects underlying this technique, making it accessible to a broader audience. The article qualitatively describes the fundamental concepts of multiphoton microscopy, particularly focusing on two-photon excitation. It explains how the simultaneous absorption of two (or more) photons leads to localized signal generation at the focal point, enabling optical sectioning and deeper penetration into scattering biological samples. It also highlights the role of turnkey mode-locked laser systems in making this technology more user-friendly. Researchers across various biological disciplines, including cell biology, neurobiology, and developmental biology, can benefit from this introductory guide. It helps them understand the advantages of multiphoton microscopy for specific experimental designs, such as imaging in live animals or thick tissue sections, where its ability to image deeper and with less photodamage is crucial. Beyond two-photon excitation, the article may briefly touch upon other multiphoton approaches like three-photon excitation and second harmonic generation (SHG) imaging, expanding the reader's understanding of the broader multiphoton family of techniques. It also discusses the limitations of the technique and provides examples of experiments where it offers significant advantages over other microscopy methods, serving as a practical resource for researchers considering its application.