Some clothing is sewn with threads made from cotton, rayon, or other natural fibers, while others are sewn with synthetic thread. The advantage of these natural or dyeable threads is that when you dye a garment sewn with them, the thread absorbs the dye just like the fabric and blends seamlessly. However, most clothing is sewn with synthetic thread because natural threads like cotton or rayon may not hold up as well through repeated washings. Look for garments with natural or dyeable thread if this is important to you.