We asked more than 200 teachers,children's authors,and children's literature experts to name the best picture books ever.We made a list based on their advice.Here are some of the books in the list.

    If You Give a Mouse a Cookie by Laura Numeroff,illustrated by Felicia Bond

    Who it's for: Grades PreK-2

    What it's about: Oh,that hungry mouse.Once you give him the cookie,he will ask for a glass of milk,and then a straw（吸管）and then...The action is unstoppable!In the end,the mouse and the boy that gives him the cookie (and perhaps the reader) are extremely exhausted!With terrific pictures and a wonderful lead character,this book shouldn't be missed by little kids.

The Other Side by Jacqueline Woodson,illustrated by E.B.Lewis

    Who it's for: Grades 1-4

    What it's about: This is a story about a fence（篱笆）that divides a white neighborhood from a black one and two little girls whose need for play and friendship allow them to cross it.It has a very deep theme.

Owl Moon by Jane Yolen,illustrated by John Schoenherr

    Who it's for: Grades 1-5

    What it's about: A classic example of child's expanding a simple walk into a glorious adventure.As a girl and her father hike through the moonlit night,the creatures they come across become exciting companions（同伴）for their owl hunt.

    The Snowman by Raymond Briggs

    The only wordless story on our list.

    Who it's for: Grades PreK-2

    What it's about:A great book to lead a child into reading.A fanciful story of a boy who makes and then befriends a snowman who both enters his world and takes him out for fun.

    Everybody hates it, but everybody does it. A recent report said that 40%of Americans hate tipping. In America alone, tipping is a $ 16 billion-a-year industry. Consumers acting politely ought not to pay more than they have to for a given service. Tips should not exist. So why do they? The common opinion in the past was that tips both rewarded the efforts of good service and reduced uncomfortable feelings of inequality. And also, tipping makes for closer relations. It went without saying that the better the service, the bigger the tip.

    But according to a new research from Cornell University, tips no longer serve any useful function. The paper analyzes numbers they got from 2,547 groups dining at 20 different restaurants. The connection between larger tips and better service was very weak. Only a tiny part of the size of the tip had anything to do with the quality of service.

    Tipping is better explained, by culture than by the money people spend. In America, the custom came into being a long time ago. It is regarded as part of the accepted cost of a service. In New York restaurants, failing to tip at least 15% could well mean dissatisfaction from the customers. Hairdressers can expect to get l5%-20%, and the man who delivers your fast food $ 2. In Europe, tipping is less common. In many restaurants the amount of tip is decided by a standard service charge. In many Asian countries, tipping has never really caught on at all. Only a few have really taken to tipping. According to Michael Lynn, the Cornell papers' author, countries in which people are more social or outgoing tend to tip more. Tipping may reduce anxiety about being served by strangers. And Mr. Lynn says, “In America, where people are expressive and eager to mix up with others, tipping is about social approval. If you tip badly, people think less of you. Tipping well is a chance to show off.”

    72-year-old Darlene Mullins recently graduated from Tennessee State University in Nashville, Tennessee. Darlene left school nearly 55 years ago in the name of love. She was studying at the college and met her husband-to-be, John Mullins, in 1962. The two knew they would marry each other the moment they met. She finished her freshman year with 25 credits and married John in 1963. Her husband graduated in 1964 and began working.

    Darlene took care of the household and was a stay-at-home mother to their son and daughter. The family lived in six states over the years, due to John's successful career in business. Darlene eventually began a career in retail as their children grew older. Though she remained busy, she always longed to finish school. She always told her children to make sure they finish what they started and she kind of felt it was time to live up to her own dream.

    John was very supportive when she told him she was going back to school. He knew the day would come when she decided to finish her degree. He told her whenever she was ready they would go. The couple moved back to Nashville in 2013 when Darlene re-enrolled. She had to adjust to the technological advances in the classroom, saying that she was determined to finish no matter how long it took. After completing four years, Darlene graduated with a degree, “I feel like God has given me a second chance.” she said' She hopes that her story can inspire others to pursue a degree.

    Madame Marie Curie famously won two Nobel Prizes, but many other women have also been awarded the prize, too. Here are their stories.

    Selma Lagerlof

    Selma Lagerlof was a Swedish author and teacher. She published her first novel, Gosta Berling's Saga, at the age of 33. She was the first female writer to win the Nobel Prize in Literature which she was awarded in 1909. Additionally, she was the first female to be granted membership in the Swedish Academy.

    Gerty Theresa Cori

    Gerty and her husband, Carl Cori, met in Prague and lived in Austria before immigrating to the United States in 1922, where the two medical doctors worked together at Roswell Park Comprehensive Cancer Center in New York. In 1947, Gerty and Carl were awarded the Nobel Prize in Physiology or Medicine, making Gerty Cori the first woman to hold the honor.

    Maria Goeppert-Mayer

    In 1942, Maria Goeppert-Mayer joined the Manhattan Project. From there, she moved on to Los Alamos National Laboratory, then to Argonne National Laboratory, where Goeppert-Mayer developed the nuclear shell model. For this, she shared the 1963 Nobel Prize in Physics with J. Hans D. Jensen and Eugene Paul Wigner.

    Dorothy Crowfoot Hodgkin

    Dorothy Hodgkin's mother encouraged her love of science as a child, and at age 18, she began studying chemistry at a women-only Oxford college. Her work on mapping vitamin B12 earned her the Nobel Prize in Chemistry in 1964.

Many families take their children on vacation. They will usually travel for a few days or weeks during school breaks. But Julie and Tim Smith planned a longer vacation with their two children. The Smith family is on a one-year trip around the world. They plan to visit 30 countries in all. Right now, the four travelers are about halfway through their trip. Ms. Smith says they are trying to see as much of the world as they can.

Mr. Smith says one of the most interesting experiences of the trip has been meeting new people. He says people have been extremely friendly, very welcoming and love their kids. Eleven-year-old Tyler says he has enjoyed learning about the people they have met. He said, "I learned in Africa that people have very different lifestyles than in America. "His sister, 9-year-old Kara, discovered that she liked Thai food. Ms. Smith says that the trip teaches the children a lot.

It took the family a year to prepare for the trip. They had to sell their house and cars. Ms. Smith left her job and her husband is using unpaid leave. They carry small bags filled with lightweight clothing and whatever else they need. Ms. Smith says she enjoys being able to carry everything she needs on her back. She says she does not miss the things she has back home. "What has become more important is making these memories as a family and taking those with us instead."

The Smiths will continue to head east for the next six months.

Where does the meat on our table come from? It usually comes from livestock like chickens and cows. But did you know that meat can also be made in a lab? US company JUST has announced that lab-grown meat could be on some restaurant menus in the United States and Asia by the end of 2018, The Independent reported. 

"These meats include chicken nuggets (鸡块), sausage and foie gras (鹅肝酱), " Josh Tetrick, CEO of JUST, told The Independent. Lab meat is sometimes referred to as "clean meat". It is made using the stem cells (干细胞) of living livestock. The cells need to be grown in a lab for a few weeks. For example, making a hamburger patty (肉饼) takes about nine weeks, CNN reported. This is faster than raising a cow, which usually takes over 20 weeks. 

The first clean meat was a beef burger that was produced in 2013, but it was said to taste quite dry. How does clean meat taste now? Clean meat supporters told CNN that they think it tastes just like traditional meat. 

Clean meat has other advantages. It is healthier than traditional meat. Meat producers can control what type of fat goes into the meat. They can produce clean meat that contains healthy fats, such as omega-3 fatty acids (脂肪酸). This kind of fat is good for people's hearts. 

Clean meat can also help to solve global warming. According to The Washington Post, about 14. 5 percent of the planet's greenhouse gas emissions (排放) come from raising livestock. That's more than the emissions from every car, train, ship and airplane in the world combined. It is predicted that switching to clean meat could lower greenhouse gas emissions by 96 percent, The Independent reported.