Femtochemistry is the area of physical chemistry that studies chemical reactions on extremely short timescales, approximately 10 seconds (one femtosecond, hence the name). The steps in some reactions occur in the femtosecond timescale and sometimes in attosecond timescales, and will sometimes form intermediate products. These intermediate products cannot always be deduced from observing the starting and end products. Femtochemistry allows exploration of which chemical reactions take place, and investigates why some reactions occur but not others. Application of femtochemistry in biological studies has helped to elucidate the conformational dynamics of stem-loop RNA structures.