In May 1988, a mother gave birth to four baby girls in Hangzhou. The city went wild with the sensational news. The babies were reportedly the first monovular quadruplets ever recorded in China's history. Experts estimate the chance of healthy monovular quadruplets to 1:13 millions. Photojournalists have been recording the growth of the quadruplet sisters with photographs every year. On May 23, the famous sisters celebrated their 25th birthday.