Dogs can smell things at concentrations of one part in a trillion—equal to a single drop in a pond the size of 20 Olympic swimming pools. That ability is put to good use by human beings. Trained dogs can sniff out explosives and drugs, even tracking missing people. They can also detect (发现) illnesses, including cancer, malaria, Parkinson's disease and COVID-19, before obvious symptoms appear. A study published in 2019,for example, suggested that trained dogs detect (发现) illnesses, including cancer, malaria, Parkinson's disease and COVID-19, before obvious symptoms appear. A study published in 2019, for example, suggested that trained dogs were able, 97% of the time, to identify blood samples taken from patients with lung cancer.

Training dogs, however, takes time. Trainers must be paid. The animals themselves get tired and bored. Dogs are not, then, a practical answer to the question of how to detect illness quickly. But fruit flies might be. Unlike dogs, they are cheap and disposable--and their senses are just as good. Along with technology tailored to their talents, they could provide economical and easy ways of detecting cancer, and also offer an alternative to laboratory tests for COVID that might be welcome in countries with limited budgets.

Giovanni Galizia is one leading researcher of the University of Konstanz, in Germany. Fruit flies smell things using their feelers, and Dr Galizia has genetically modified  (改变) his flies. When the flies get the smell of the cells with illness, a change in their brain activity can be seen under a microscope. With the help of machine learning, Dr Galizia can recognize the patterns to detect illness.

Whether this idea will come to fruition remains to be seen. Medical regulators will have to be convinced that what may seem wacky at first glance is actually practical. But doctors have been encouraged to use animals' noses to assist diagnosis (诊断) since ancient times. Having a little assistance from fruit flies might be no bad thing.

Sarah Park has known about the impact of music on the brain since a young age. The 13-year-old, who has been playing the violin since she was 4, says she noticed its positive effect on those around her, especially her grandmother, who suffered from mental illness.

Now, the Jacksonville, Florida, middle-schooler hopes to use music therapy (疗法) to help others struggling with mental illness. Her invention, Spark Care + , earned her the title of "America's Top Young Scientis" at the 3M Young Scientist Challenge on October 19, 2021.

Spark Care+ requires participants to respond to a series of questions based on the Hamilton Anxiety and Depression Scale, designed to assess the person's mental state. The device's inbuilt sensors record vital mental health indicators? such as heart rate and blood pressure. Spark Care+'s Al component analyzes the information and recommends the appropriate music to help lift the participants' spirits. It also monitors its impact on the listeners.

Sarah Park hopes to make her invention accessible to all. The ninth-grader hopes to turn it into a wristband with inbuilt sensors, a heart-rate monitor, and Bluetooth. She also wants to build an app to make Spark Care+ accessible to everyone. "I hope to be able to distribute it around the world to people of all ages," Park says.

In addition to being an inventor, Park is also a musical prodigy who has won several violin competitions, including the Florida state championship. She also plays the piano and is a math champion. The teen hopes to be an innovator and researcher in the medical field using technology and robotics. Her advice to other young scientists? "Dream big, ask questions, and anything is possible."

Paul Durietz is a 76-year-old social studies teacher from Illinois. On September 1, he set a Guinness World Record for the world's longest teaching career. Mr. Durietz has been teaching for 53 years—since he was 23 years old. 

Mr. Durietz has known since he was young that he wanted to be a social studies teacher. Social studies is the study of history, and how people, countries, and cultures are connected. He became interested in history after hearing stories from his father, who fought in World War II. On his mother's side of the family, he had connections to a famous person from English history. 

Mr. Durietz got his first teaching job at Woodland-Middle School in Gurnee, Illinois in

1970. Ever since then, he's been teaching social studies at the same school. He says he loves sharing his knowledge of history with students. "Teaching is never boring," he says. "Every day is different."

Things have changed a lot since he began all those years ago. When he started, the only way to make copies was with a "ditto machine", which used a stinky, purple ink. Mr. Durietz wrote on a blackboard with chalk, and the students used paper textbooks. These days, he and the students use computers and digital whiteboards. 

Though technology has changed a lot since he began teaching, Mr. Durietz says the students are still pretty much the same— except that now they have cell phones. 

With or without technology, Mr. Durietz has used creative activities to help his students learn. For example, he has organized virtual field trips, geography contests, and special days about the US Civil War. He has even organized fake（假的）elections at school to help his students learn about politics. He says these activities are some of the ones that he and his students enjoyed most. 

Mr. Durietz says people who want to be teachers should make sure they are patient with their students. He also encourages them to choose subjects that they care deeply about.