Molds are fungi that multiply by letting their spores float in the air until they latch on to something they can migrate on. The thing about molds is that their spores are not visible to the naked eye. It won't be until they have grown.
Floating mold particles can perch on anything inside your home. And because they haven't attached themselves to anything, it's easy for you to inhale them. The scary part is that once it's in your system, it can cause a gamut of health complications, most of which are respiratory tract-related.
Keep in mind that molds thrive in damp and humid environment. This makes your bathroom and laundry area likely areas for growth. Using dehumidifiers will significantly lower your chances of having mold growth inside your home.