Li Xiulan says that for all of her 73 winters in China's frigid northeast, her best weapon against the biting cold has been a pile of bricks. Like millions of northern Chinese, Li wakes up every morning on a kang - a traditional brick sleeping platform heated from below by burning straw or coal during the long, dark winter months.
"Without the kang, winter would be unbearable," she said, bundled in layers of sweaters and warming her hands before the gentle heat of the kang in her grandchildren's bedroom.
Environmentalists worry that kangs waste energy and add to choking air pollution. But people here say it's the only way to survive in China's version of Siberia, where the winter sun sets at 3 p.m. and temperatures can plunge to 40 below zero.
For centuries, the kang - pronounced "kahng" - has been the center of winter life in the northeast. Families crowd together on them to sleep under mountains of quilts. Children play on them during the day. Parents do as many chores as they can on them.
In the countryside, kangs have survived the arrival of electricity, mobile phones and the Internet. Families gather on them to watch satellite television and DVDs.
Scientists warn that kangs waste fuel, pollute the atmosphere and endanger the health of farm families by releasing carbon monoxide and other dangerous gases indoors.
Towns throughout the northeast are wreathed in smoke as families fire up their kangs for the evening. More prosperous homes emit the fetid odor of burning coal.
"In order to protect the environment, the government should encourage and guide farmers to give up using kangs," Wang said. "But the kang cannot be phased out in a short time because the farmers in these areas depend on them."
The government and environmental groups have sponsored research to produce alternatives using such things as natural gas from decomposing farm waste.
But for many families, the kang is close to perfect.
"When it gets cold, everyone has to have a kang," said Zhou's father-in-law, Dou Zhiquan, 56. "Without one, you can't survive the winter."