English: Map of global MEG systems. MEG systems from Biomag Central (2017) were categorized according to the developmental period they are built to study. This map is not exhaustive but provides a general overview of how many systems are dedicated to each developmental period worldwide. Whereas many systems can record MEG signals from adults or children (cyan), only nine MEG systems that we know of are capable of recording from infants (yellow). Even fewer systems (four) are capable of recording from fetuses. Of these, two are SARA systems (red) and two are general system for recording fetal biomagnetic signals, including magnetocardiogram (MCG, magenta). The global scarcity of MEG systems capable of recording from fetuses and/or infants underscores the difficulty of studying this developmental period. However, next generation MEG systems based on optically pumped magnetometers (OPMs) may improve the availability of fetal and infant MEG (Wakai, 2014) by allowing for ad hoc recordings that do not require custom-built cryogenically cooled devices. Image and figure description originally published in Frohlich et al. 2023 Neuroimage: https://doi.org/10.1016/j.neuroimage.2023.120057