One hundred and one - introduction to science

In the American education system, 101 courses indicate an introductory, basic level: 'Biology 101', 'Economics 101'. The expression 'X for dummies' has evolved into 'X 101' — a universal synonym for the basics of any discipline.

Binary number 101 = 1×4 + 0×2 + 1×1 = 5. The alternation of ones and zeros makes 101 an elegant example for explaining binary arithmetic.

'101 Dalmatians' is one of Disney's most beloved animated films (1961). The story of Cruella de Vil and stolen puppies became a classic and gave rise to a franchise of films and sequels.

January 1st — the first day of the year in the Gregorian calendar, celebrated as a public holiday in nearly every country.