The geomagnetic field has been continuously monitored from low-Earth orbit (LEO) since 1999, complementing ground-based observatory data by providing absolute calibrated scalar and vector measurements with global planetary coverage. Such absolute magnetic vector data have proven critical for our ability to make progress in our understanding of the many sources of the Earth's magnetic field, their dynamics and the way they interact. Combined with data from adequate complementary payloads, these data can also be used to monitor the ionospheric environment. The information they provide is also massively used for many applications, ranging from orientation needs to space weather monitoring as well as, e.g., reconstructing Earth's crustal and mantle electrical conductivity. Ensuring continuity and improvement of such observations is therefore critical. Here, we will provide an overview of the current status and many science objectives of the NanoMagSat project, which aims to deploy and operate a new constellation concept of three identical 16U nanosatellites, using two inclined (approximately 60°) and one polar LEO, designed to complement and ensure continuity of the ongoing ESA Swarm mission at a much lower cost, and to also provide new science opportunities. This mission was proposed to ESA within the context of its Scout program, and is currently undergoing a 18 months Risk Retirement Activity phase funded by ESA, due to end in July 2023 and aiming at implementation for a launch possibly as early as 2026. The three-satellite constellation design is such that all local times at all geographic locations between 60°N and 60°S will be covered in a little more than one month, much faster than Swarm, which the NanoMagSat is also designed to complement for even better coverage, should Swarm still be in operation at the time of launch. Each satellite will carry an innovative payload including an advanced Miniaturized Absolute scalar and self-calibrated vector Magnetometer (MAM) combined with a set of precise star trackers (STR), a compact High-frequency Field Magnetometer (HFM), a multi-needle Langmuir Probe (m-NLP) and dual frequency GNSS receivers. This payload suite will acquire high-precision/resolution oriented absolute vector magnetic data at 1 Hz sampling rate (for global magnetic field modelling purposes), very low noise scalar and vector magnetic field at 2 kHz (for ELF signal detection and down to decameter-scale local electrical currents monitoring), electron density data at 2 kHz (for very small scale plasma density investigations), as well as electron temperature at 1 Hz. GNSS receivers will also allow top-side TEC and radio-occultation profiles to be recovered. Possibility of using the STRs to further recover energetic proton omnidirectional flux (above 100 MeV) is also considered. This presentation will also report on the way the science preparation of the project is currently moving forward with the help of its growing Science international team. On the longer term, NanoMagSat aims at forming the basis of a permanent collaborative INTERMAGSAT constellation of nanosatellites for low-cost long-term monitoring of the geomagnetic field and ionospheric environment from space, complementing the INTERMAGNET network of ground-based magnetic observatories.