Motivated by striking properties of the well known Fibonacci wordwe consider pictures which are defined by this word and itsvariants via so-called turtle graphics. Such a picture can bebounded or unbounded. We characterize when the picture defined bynot only the Fibonacci recurrence, but also by a generalrecurrence formula, is bounded, the characterization beingcomputable.

We show that any positive integer is the least period of a factor of the Thue-Morse word. We also characterize the set of least periods of factors of a Sturmian word. In particular, the corresponding set for the Fibonacci word is the set of Fibonacci numbers. As a by-product of our results, we give several new proofs and tightenings of well-known properties of Sturmian words.

We survey several quantitative problems on infinite words related to repetitions, recurrence, and palindromes, for which the Fibonacci word often exhibits extremal behaviour.

The LS (Look and Say) derivative of a word is obtained by writing the number of consecutive equal letters when the word is spelled from left to right. For example, LS( 1 1 2 3 3) = 2 1 1 2 2 3 (two 1, one 2, two 3). We start the study of the behaviour of binary words generated by morphisms under the LS operator, focusing in particular on the Fibonacci word.