Plant-based milks are increasingly gaining popularity as alternatives to traditional dairy, largely due to rising consumer interest in lactose-free, vegan, and environmentally friendly options. This chapter examines the main sources used in producing plant-based milks, such as cereals (oats and rice), legumes (soybeans and peas), nuts (almonds and cashews), and seeds (flax and hemp). Each category brings its own set of nutritional benefits, flavors, and functional traits. The typical production process involves soaking, grinding, filtering, and homogenizing the raw materials, often followed by fortification, although the methods can vary depending on the plant source. Recent innovations in processing techniques—like enzymatic treatments and ultra-high-pressure homogenization—have helped improve the texture, stability, and nutritional value of these products. However, challenges such as managing off-flavors, preventing sedimentation, and enhancing protein content still need to be addressed. A deeper understanding of plant sources and continued improvement in production methods will be crucial for meeting the growing demand for high-quality plant-based milk alternatives worldwide.