21st-century skills are mentioned throughout the world as the goal to be reached by nations' educational systems as well as by current and future citizens everywhere in order to fit in the future labor market and society. The purpose of our review is, firstly, to find out the definitions of the so-called 21st century skills so that we can have clear teaching and learning goals. Secondly, the relations that can be found between the recently objectified STEAM learning environments that are claimed of being able to develop such skills. We are seeking for those new environments to reach the abilities and skills as we are on the verge of different and innovative teaching and learning systems, methods and techniques. We hope to contribute to the discussion on the current entries (students, teachers, environment), processes needed (learning/teaching/practicing of subject or core knowledge and abilities & skills) and desired outputs (empowered and adapted individuals) for the 21st century educational systems worldwide.