Starting a sourdough starter is a rewarding and delicate process that requires patience and attention to detail. By day 4, your starter should be showing signs of life such as bubbles and a slightly tangy aroma, indicating that the wild yeast and bacteria are becoming active. Maintaining a consistent feeding schedule with equal parts flour and water is key to nurturing a healthy starter. Pay close attention to the temperature of your environment; a warm spot around 21–24°C (70–75°F) is ideal for fermentation. At this stage, it's normal for the starter to have a slightly sour smell, which will develop further during the fermentation process. If you notice any discoloration or strong odors like rot, discard the batch and start fresh. Make sure to use unchlorinated water and organic or whole grain flours to give the microbes the best possible environment. Day 4 can be a pivotal moment when the starter doubles in size and becomes bubbly and airy. This transformation indicates that your starter might soon be strong enough to bake with. Using your starter to craft sourdough bread can yield delicious results with a wonderful texture and tangy flavor that exemplifies natural fermentation. Embracing the process and observing your sourdough starter grow can be truly satisfying for bakers of all levels.