Two-dimensional (2D) magnetic van der Waals materials and their heterostructures are emerging candidates for ultralow-power and ultra-compact spintronic device applications. Although the Mermin-Wagner theorem predicts suppression of long-range magnetic order at finite temperatures in such 2D materials, recent experiments have demonstrated the existence of long-range ferromagnetic ordering in bulk van der Waals materials at the single layer limit. In particular, our recent discovery of the strong room temperature ferromagnetism in epitaxially grown transition metal dichalcogenide (TMD) monolayers of VSe2 grown on various van der Waals substrates has the potential to transform the fields of spintronics and quantum computing. In this talk, we will present research progress in 2D magnetism, including our new findings of tunable exchange bias effect and room temperature light-controlled magnetism in monolayer heterostructures, as well as the development of a new class of highly sensitive magnetic sensor using this single layer magnet. Opportunities and challenges in 2D magnets research will be discussed.