The current study is the first to examine the role of exploration in play milestones development using a multi-measure micro-analytic approach. Fifteen infants, between the ages of 8 and 17 months, were observed in their natural home environment once a month for a one--hour session; their spontaneous mouthing and fingering and their play level with objects were recorded. Four types of play acts were coded: single--object play, single--object sequences, multi--object play, and multi--object sequences. The relative degree of usage of each type of behaviour at each month was examined. The results show that a combination of mouthing and fingering supported most play acts. Mouthing alone supports the simplest type of play act while fingering supports an advanced type that involves a single or several objects combined in sequences of actions. The benefits of exploring the object orally and manually in the development of play behaviour are discussed.