Meet Chris and Martin Kratt, two brothers who turned a love of animals into an amazing career! They have produced, written, directed, and starred in several PBS series and specials over the years. Most recently, they have become known for PBS's smash hit animated show . Along the way, they traveled the world and encountered incredible creatures, all while combining science education with fun. Boys and girls ages 4 to 7 will this Step into Reading biography of two brothers who know how to live life on the wild side. Step 2 Readers use basic vocabulary and short sentences to tell simple stories. For children who recognize familiar words and can sound out new words with help.