In Photos, when you are viewing your pictures as Thumbnails, tap the share/action icon (box with arrow coming out) and select up to five photos. Then tap the Share button at the top left and choose Email.
Alternately, when viewing a photo at full size tap and hold for the popup menu, then choose Copy. Go to Mail, tap and hold in the body of the email, then paste. You can move back and forth doing this as often as you like, but hold in mind the bigger you make the email the slower it will be to send.
Once an email with photos goes over a certain size you may see a size estimate (Images: x.xMB) to the right of the CC/Bcc, From line. Tap on it and you can choose to send smaller versions of the photos.