In Japan, the maintenance and renewal costs of the extensive road infrastructure, including bridges and tunnels, are estimated by the Ministry of Land, Infrastructure, Transport, and Tourism to be able to save 85 trillion yen over the next 30 years if addressed through 'preventive maintenance' before any malfunctions occur, as compared to 'reactive maintenance' after problems arise. To achieve this preventive maintenance, I propose to use electromagnetic waves to visually inspect the internal structure of infrastructures in three dimensions dynamically, a technique I have named 'Four-dimensional Transparentization.' The key to this technology is a device called 'ground-penetrating radar.' Recently, vehicle-mounted radars that can acquire high-density three-dimensional information of the road interior and the inner walls of structures in the direction of travel, perpendicular to the direction of travel, and depth, at intervals of several centimeters, while traveling at speeds of over 80 km/h, have become more accessible, and we are actively utilizing them. In this presentation, I will introduce the latest developments in transparentization technology using ground-penetrating radar.