Starting a sourdough starter can be a fascinating process filled with little surprises each day. On day 4, like in this update, it's common to check the aroma and texture to ensure the starter is healthy and progressing well. A pleasant sour smell or even a mild tang is a good sign, while an unpleasant rotten odor could indicate problems that might require discarding and restarting the starter. Personally, I've experienced the anticipation around day 4 during my sourdough journey. It's a turning point when you can detect the natural yeasts beginning to thrive. At this stage, feeding the starter regularly with equal parts flour and water while maintaining a consistent temperature helps the fermentation process. The mention of "Masa madre" (mother dough) reminds me of traditional bread-making methods that rely on natural cultures, which not only create unique flavors but also promote digestibility. If you're new to sourdough, be patient and cautious. Sometimes, small bubbles and a slightly sour smell are normal, but if you notice mold, pinkish hues, or a putrid smell, it's best to start over. Also, documenting each day's changes, as done here, is a useful habit to understand your starter's behavior. Keep your starter in a warm place, away from direct sunlight, and stir it daily to incorporate air. With consistent care, your sourdough starter will soon be ready to bake nutritious and delicious bread with a crispy crust and rich flavor.