1) The concept of 3D printing, also known as additive manufacturing, was first introduced in the 1980s and has since revolutionized prototyping and small-scale production.

2) The highest-grossing concert tour of all time is U2's "360° Tour," which earned over $735 million in ticket sales.

3) The concept of proportional representation, used in some electoral systems, aims to ensure that political parties' representation in government aligns more closely with the proportion of votes they receive from the electorate.

4) The word "pizza" contains two vowels: I and A.