X-raying Narrow-line Seyfert 1 galaxies

Since the 1990s, Narrow-line Seyfert 1 galaxies (NLS1s) have been known for their extreme X-ray behaviour. They exhibit the largest amplitude variations, biggest soft-excesses, strongest signatures of relativistic reflection, and potentially powerful outflows. However, the origin of such behavior and how NLS1s fit in the broader context of Seyferts are still debated. Here, we will highlight recent X-ray works of NLS1s, examining both sample studies and deep investigations of individual sources. In combination, we attempt to draw a picture of Seyfert unification including NLS1s. We will further consider what is in store for NLS1 research in the era of high-resolution spectroscopy with XRISM and ATHENA.