Yes, teacup yorkies stay small their entire lives. When fully grown, teacup yorkies are only 5–7 inches (12.7–17.8 cm) tall and weigh 2–4 lbs (0.9–1.8 kg). They are far smaller than regular Yorkshire terriers, which typically weigh 6–7 lbs (2.7–3.2 kg) when mature.
Teacup yorkies were bred to stay adorably tiny, and they usually reach their maximum size within the first twelve months.
Note that they are more prone to injuries and health issues due to their small size, so they require extra care and attention to stay healthy.