Clickers? More technically, maybe personal response systems. For a long time these devices have been used in teaching, for student engagement, in guidance by the instructor, on innovation, in improvement of the catalysed learning process. Even if you don't have enough clickers for all your students and the associated logistics, you can still work quite successfully and without complexity using free online services and the students' laptop, tablet or smartphone.

Republication of the article originally published in the University Education section of SEBBM Journal, issue 179, March 2014 (the Journal of the Spanish Society of Biochemistry and Molecular Biology). It is republished here after the journal's original website was taken down.