Scientists have found that it can take as little as three seconds to determine if a person is the sort of individual you’d like to spend more time with at a chemical level. To truly fall in love, however, there is no set time period simply because love is such an individual thing and there are many different kinds of love. Most often it can be explained by saying you’ll know when you’re in love and if you’re wondering if you are, you probably aren’t in a deeply romantic love at least.